One point on diesels that is more than a detail is the annoying MTH practice of selling cab units ONLY in ABA sets, regardless of how the railroads employed them in real life. With passenger units especially, there are ABA sets out there for railroads that never owned a B unit. Those of us with smaller layouts have to leave the B unit in the box to keep train length down. The FT's were only sold in ABA sets, although most FT's were in drawbar-coupled AB pairs. Very few add-on B units were made, so it can be pretty difficult to put together a proper ABBA set if you didn't pre-order. And yes, I know a few railroads ran FT's in ABA configuration - but the vast majority ran as ABBA, or sometimes just a single AB pair.
Another point a couple of people have raised is that rising expectations go with rising prices. Lionel's diesel prices are close to 3rd Rail territory, and MTH aren't cheap either. Steam engine prices are even higher. Paying those prices, we expect more detail and more fidelity to prototype. I will put up with things on a $300 engine that I will not consider on a $700 engine.
