Parts of this have been done in various threads and there was a recent thread on the general question of DCS vs. legacy. The goal here is different - it is for people who run conventional and are thinking maybe they need to get into the app / tablet thing and can benefit from what I experienced. One of the frequent suggestions from forumites is to consider the locos you like and use that to guide you in these decisions. Unfortunately for me, I like a number of the MTH locos (such as RF&P- which I don't think Lionel has produced any) and I also like Lionel sound and other features. So I was stuck considering both manufacturers options.
I have run my locomotives in conventional mode in the past and thought it was time to move into the current generation of tablet operation. All of the following is based on experience using a kindle. Who wants to look at a phone screen? Not me- too small! So here we go.
1) The easiest transition with Lionel was to purchase a blue tooth locomotive. I have a number of lionchief plus locos (prior to Bluetooth) and this shows screen captures for the NS SD60 using the Bluetooth app. It is a more complete, full featured parallel to lionchief plus. It is rock solid, recognizes the loco without fail, never misses a beat and does the basics that are fun and functional. I am looking forward to the next generation of 2.0 to see what it adds. You may have seen these shots but the interface is simple and intuitive and best of all- FREE! (of course you need to buy a Bluetooth loco.)
2) For MTH, we all know they are moving to the app so I sprung for the wifi system with the TIU. It is a good value combination but still costs over $300. It is a full featured system, I assume with similar features to what you would get if you purchased the handheld device they are discontinuing. It has more options than the current Lionel Bluetooth - I also spent $30 or so for the additional features for the app. Comparing this to the Bluetooth is apples versus oranges since this system will be MTH's full featured system before long when they stop manufacturing the hand held controller. For me, features like doppler, rev-up-down, boost etc. are not very useful. Maybe this is the luddite in me? Also presenting a screen with a long list of unidentified custom sounds is also not very useful. (Did I miss something explaining these?) I do like the scale MPH- cool! And varying smoke levels are nice compared to smoke on or off on bluetooth. A big plus, my old PS 2.0 locos work with this too. Relative to simplicity, there are extra steps compared to Bluetooth. You need to log on to the DCS wifi if you choose this route and in an hour of running trains there is typically a glitch (lost locomotive or one that is difficult to shut down, etc.). Otherwise it is good and fun.
3) the moral to the story, Lionel Bluetooth is rock solid but limited features (we will see what 2.0 brings). MTH wifi is full featured but for me, many of these options were not useful plus the system costs between $300 and $400. Am I happy with what I did, yes indeed. I am glad I have both capabilities since I like my RF&P MTH locos and I like my Lionel Bluetooth locos, but you need to make the decision based on what you like and your operating expectations.