Can't believe how time flies! We got involved in toy trains Thanksgiving weekend 2011 when we bought the Polar Express set. In these 6 years, we've researched and learned through trial-and-error. We eventually undertook building a 33 x 16 layout that now, almost 70% complete, we've dismantled in favor of our upcoming smaller layout that will provide a better balance with recreational space in our cellar. For any new people to the hobby, I offer this as a sort of "what I wish I knew that no one really mentions" commentary. It's just my opinion and I welcome others to share their experiences.
Trackage
So many threads on this subject, but the thing rarely discussed is functionality. We used Lionel's FasTrack and MTH's Realtrax on our first layout, a temporary 4x16 effort. When we decided to build our "permanent" 33x16 layout, we decided they were both too noisy and neither was very realistic looking. So we bought a little bit of RCS, Gargraves, Atlas 21st Century and MTH ScaleTrax to test them all. We found that the solid rail options, Atlas and MTH, were the quietest and most realistic looking in terms of rail shape and scale of ties. We ultimately went with Atlas because it looked the best to us, was rugged, and offered every curve size we would need. In retrospect, while we have had zero electrical issues, the other track options are probably all more theoretically sound from an electrical conductivity standpoint. The Gargraves and RCS have long plug-in pins to ensure a good connection, unless you connect/disconnect them repeatedly, or the track isn't secured and has play. And the MTH version has hidden spring loaded large copper touch points that could not offer a better connection.
Turnouts
We have mostly Atlas but some RCS. In our experience, Atlas is plug and play and incredibly easy to set up and use. Available turnout options are OK but not great. The only curved version is 054/072. Few or no yard options. Recent upgrades alleviated most prior operating issues/concerns. Our only negative with the new turnouts was the throw rail not traversing all the way across. I was told the small plastic housing piece that sits atop the bar that controls that rail sometimes is too tight and causes friction, causing this issue. Can't comment, as they are all packed away for now until we start our new build.
RCS are very nice pieces. We use ours manually but some folks at the club said they had to upgrade motors for throw rail to go completely across. Trains move very smoothly through these units, although I have the 4-way yard turnout and trains routinely "thunk" through the frog on the non-diverting leg. RCS also makes a ton of options, many more than what's available from any other manufacturer, allowing so much flexibility.
Command Systems
I believe DCS is the most advanced command system on the O scale market. It is also the only true two-way command system in O Scale. It is also the least expensive alternative, especially if you intend to add more handheld controllers. DCS handheld units require batteries, which, if you don't use rechargeable versions, can slowly create cost creep. Operation, in our experience, is finicky and spotty. We've had engines respond perfectly for a time and then not respond on the exact same track they've traversed for the last 10-45 minutes - often with a illogical fault code such as "engine not on track," while the train is still running. And this is in spite of us strictly following the special MTH wiring recommendations. As stated, there are special wiring considerations that are time-consuming and costly if you have anything more than a basic small loop. When DCS is working properly, however, it offers the most features and, therefore, the most play value possibilities.
We've found, and consensus at two local clubs is, that Legacy and TMCC "just work." Incredibly reliable. With respect to the current system, Legacy, while the controller knobs and buttons are all easy to operate, not all Legacy features and personalizations are intuitive to the novice and require review of the manual or asking one of the pros on this forum for help. Wiring is incredibly easy, quick, and much less expensive than DCS. Ownership cost is higher than DCS, especially if you intend to add handhelds. Each additional Legacy handheld is sold only as a unit with an additional base unit, making for a much more expensive proposition than DCS. Legacy uses rechargeable batteries, however, which over time could offer a cost savings over DCS, if you use disposable batteries with DCS. Legacy is a one-way communication system although there is now a band-aid for some two-way functionality if you purchase the LCS track.
Steam Locomotives
MTH's smoke output is prodigious and a huge attention getter. If you like huge plumes of smoke from the stack, without doing any modifications, MTH is tops. Other than their Big Boy, however, the smoke effects are limited to stack smoke only. The sound system is good and MTH tried to ensure each locomotive uses the correct whistle sound. Some tenders reverberate and buzz when the whistle is sounded. The detail level on their Premier line locomotives is very good considering the price point is the lowest of the majors. These locomotives were clearly well engineered, or perhaps over-engineered, providing a high level of craftmanship, but also somewhat unforgiving if the (tricky to connect and disconnect) "wireless" drawbar isn't treated right or too much smoke fluid is added. Also, sometimes finicky, with locomotives turning themselves off. With DCS, many sounds are automated, adding to the realism. As an example, you don't need to fire any command to hear the engineer and others intermittently talking, and the locomotive will automatically switch to a clikety-clack when it sustains speeds over approx. 35 smph for some short period of time.
Lionel offers good detail, great sound and they are very rugged units. The sound package, however, is "generic" in that many locomotives share the same sounds. Hook-up between tender and locomotive is the hobby's easiest. If you like smoke effects, look no further as Lionel, depending on the offering, has stack smoke, whistle smoke, Dynamo, steam chest, blow-down. If you like massive plumes of smoke, or you like the stack to pump out smoke in a prototypical staccato style, however, upgrades will be necessary. I've seen some good smokers, but the default is that, for most smoke features other than stack (which is ok), they generally put out wisps of smoke. People argue this point, so find out for yourself - check out Youtube videos - many people who do reviews will even state that they are putting the engine in front of a background that will allow you to see the smoke effects. Operation is usually smooth from speed step 1 to top speed. My biggest applause is that Lionel continues to advance the art by introducing new operating features and better sounds to enhance play value.
Sunset models offer the highest level of detail of those mentioned here (although some of MTH's Euro steamers might give some Sunset models a run for the money). The most accurate looking steamers. They use TMCC, however, which is technically last-generation command technology, although it is constantly tweaked for optimization. Really good slow speed operation and nice smoke output. Nice bulletproof drivetrain with a large motor. To my knowledge, Sunset offers only stack smoke.
Diesel Locomotives
Lionel has always been a smooth operator for us. Good looking models, good detail level. Sound system is great. We only have Vision versions, and these have incredibly detailed cabs.
Our two MTH Premier ES44s have been unstoppable performers with a ridiculous level of functional detail, including many functional doors (even in the locomotive nose). Our RK Scale RS-1 and several Imperials all arrived with, or soon developed, very jerky operation. Visits back to MTH do not solve the issue. If you get a good one, it's the best fun value out there and the pulling power is prodigious.
Atlas: very solid constrution, a lot of prototypical exterior detail and good pulling power. Versatile in that you can buy as many A and B units separately as you'd like. It does, however, rely on TMCC and this isn't really an issue with diesels, but recognize that you aren't buying latest generation technology.
Sunset - very smooth and a nice level of prototypical detail. I like the fact that there is one large can motor generating the pulling power. Seems this obviates any jerky performance that would be caused by two smaller motors being out of synch with each other. I also like the smoke output. It runs on TMCC, similar to Atlas. Like Atlas, you can separately buy as many A and B units as you'd like, but because all are powered, your price increases approximately 100% for every unit you add to your motive consist.
Passenger Cars
They range in price and protoypicalness. Least expensive scale-ish cars are produced by MTH. They offer a good level of detail - interior and exterior - on very well made cars. Premier cars include full overhead lighting, 10 really nice looking figures, sometimes beautiful circular interior stairways on full vista cars, and perfect paint on exterior. They are, however, all cookie cutter (like Lionel) in terms of exterior detail and interiors. And, they remain 18" long when the prototype might actually require a 21" length. These cars are, to us, the best value in the hobby - a solid, perfectly functioning car with a nice level of detail at a very attractive price.
Lionel now offers both scale-ish and scale length cars. They have nicely detailed exteriors and interiors. These cars are equipped with full overhead lighting, a nice level of exterior detail, nice looking passengers and detailed interiors. The newer 21" cars lack interior little people, but they offer more prototypical size, close coupling, constant voltage full overhead lighting and some offer a Railsounds car, which puts play value in another class. If you favor things like truly prototypical windows and such, you might be a little disappointed.
Sunset - scale cars with beautiful exteriors and interiors. Some say these are the most prototypical cars available. If that means the cars have the most realistic-to-the-prototype window shapes, trucks, and scale sized interior seating that is (presumably) arranged in the configuration of the prototype, then that might be true. These cars have an interior overhead lighting system, however, that only sheds light on approximately the middle 50% of the interior, with the 25% on each end sitting in darkness. This is not prototypical. Each car has flicker-free lighting. Due to material choices, windows that are tinted on the prototype are crystal clear on these cars. So, they look like truly real windows, just sometimes not windows found on the prototype. Cars are relatively closely coupled adding to the realism. Price is on balance the highest of the basic competition (Lionel, MTH and Atlas). If Sunset were to work the 'bugs" out (some of which are non-issues on even entry level models from their competitors) I'd consider their products much more regularly. Another benefit is that Sunset offers many options that aren't available elsewhere. This adds character and uniqueness to your pike.
Atlas - scale cars with beautifully detailed exteriors and interiors. The California Zephyr set epitomizes these qualities. Price is between Lionel and Sunset. The exteriors are amazing. The interiors, while each is made of what looks like one (perhaps non-prototypical plastic configuration?) piece, are very detailed, despite no little people occupying the chairs. If you want to add little people, it is challenging, so having ghost trains is the only negative to this set. Relatively close coupled cars helps add to the realism. Overhead lighting illuminates the entire interior. You can add batteries to each car's underside, which ensures flicker free operation and heavier, smoother, more real looking operation. Interior lights can be toggled on/off. Windows have the right tinting. The windows even have blinds or shades! It's a really nice extra touch that makes a big difference and exudes quality and value, and realism.
Dealers
I'll note that in six years, I've found that the best ways to decide on who is a "top" dealer are: (a) most knowledgeable on the products; (b) competitive pricing: and (c) most importantly, by customer service when something goes wrong. In essence, a good dealer doesn't happily take your money at the sale point and then send you off to deal with the manufacturer when there is an issue with what the dealer sold you. He inserts himself to take the headache on himself, or at a minimum, helps resolve. After all he's the one that's supposed to be building the long term relationship with you for his future success.
If you've found any part of this helpful, I'm grateful.
Peter