I'm starting think about building up a "collection" of conventional engines and cars to run on a layout I hope to build with my kids soon. Looking at what's for sale, it seems to me that the Limited and Service Station sets might represent a good value compared to buying engines and cars individually. As far as I know these sets (at least with conventional control engines) spanned the late 70's to late 90's, and there were a lot of them. I think all of the sets I have seen had die-cast trucks on the rolling stock, while a lot of the rolling stock Lionel made during at least some of this period had plastic trucks. The diesel engines included with the sets have different features: one or two motors, mechanical vs. solid state e-unit, diesel horn vs. no horn. A lot of the diesel engines have stamped steel railings while others have wire railings, which look less kid-proof to me.
Are there any rules of thumb about better or worse products in terms of years or features or particular sets? Durability/reliability are my main concerns. Thanks for any guidance you can share.