I'm currently in a bit of a debate. The last version of Trainz that I had the pleasure of running was the 2006 edition. It's on my gaming computer, which I haven't even booted up in 6+ months. I'm getting it upgraded soon. But more to my point, I'm going to upgrade to either Trainz 2010 or 2012. Maybe even both.
I will say that one of the things I enjoy most is creating prototypical routes in Surveyor. My "baby" is a 150-mile route in Indiana that I seem to drum up in each version of Trainz. I would like some different opinions or views on both editions. I am taking into consideration many things. Among them are backwards compatibility, quality of graphics, performance levels, etc. Any insight would be appreciated!