If you
really want a product that's more purebred model train sim, I'd suggest (and I can't even believe I'm suggesting it) that you buy a copy of Ultimate Trainz Collection. However, it's quite old, doesn't run as fast as newer versions do, and precious little content is being made for it (one author that still produces UTC content is ish6.) There is also no official support for steam locomotives; unless you run them in DCC mode they will act like diesels and have diesel controls.
However, I'd
only recommend buying it if you can live with all of the above conditions. The newer versions of Trainz are undoubtedly far better in terms of content, graphics, and speed; they're just not focused towards virtual model railroading as much as UTC was/is.
Believe it or not the Trainz series was originally conceptualized, and designed, as a
model railroad sim. TRS2004 was where the proto stuff started seeping in and the Trainz series lost its focus. It is now solidly focused towards proto operations.
If you can't live with the above conditions I'd suggest getting a copy of TRS2004 (again, I can't believe what I'm typing

). It's still an old version, and still lacks the polish and content that newer versions offer, but it's also very stable and considerably less fickle and temperamental than TRS2006 (and TC, from what I've seen an heard, although I have not bought TC.)