I've tried... Ooooh how I've tried.
I have given up on this game, and it's older sister, Trainz 2010.
The UI is astronomically horrible, something as simple as loading up a train and driving on a track becomes a monumental task. The amount of content in the game is great (more for 2010 than 2012) but finding the good stuff amongst all the garbage is extremely difficult. Imagine if Flight Sim X bundled together a bunch of graphically inept Freeware and cobbled them together and called them a sequel, and you pretty much have the idea of Trainz here. Yes, 2010 has a massive 51 routes, but only a few of them are actually good, and most of them have hardly any scenarios or "sessions", which are almost the only thing you can do if you don't have the time to learn how to use the editor.
For example, in Train Sim 2014 (from what I've seen, I don't own it, but I should soon!) in order to drive a train on a track, all you need to do is go to the "Quick Drive" section, choose a train, choose a route, choose a start and end point, and away you go.
In this, you need to find the route you want to play on from the GIGANTIC list (again, mainly 2010, not 2012), create a new scenario, find the massive list of locomotives, (in an insanely small text size) with extremely small pictures, plonk it down on the track, then find some carriages or freight that matches the coupler type (you can also choose a pre-made consist, but 99% of them don't actually have locomotives) plonk them down behind the loco, then save the session, go back into the main menu, find the route again, find the session again, launch the session, wait for it to load again, then you can finally drive the train, of course, you don't have an actual end objective like in TS2014. It's far too difficult and annoying to do if you don't have much time, and just want to drive your favourite Steam train around a track for a bit.
Then there's the DLC...
Yes, TS2014 has a lot of it, yes, some of it is overpriced, but they all download quickly and easily through Steam. In Trainz, not so...
If you buy a DLC on Steam, for 2012 you have to activate the CD-key in game, then you have two options. 1. Wait for it to download at less than dail-up speeds, or 2. pay *more* money, to download it faster. It's worth mentioning that I didn't even ever get the downloads to work, they just kept failing and wasting my limit amount of broadband. 2010 is a little easier... in 2010 all you need to do is put a file in a folder, then run an extended database repair, wait for about an hour, then you can play your DLC, but that implies you own Trainz 2010...
Now, I can't compare the physics of the two games because I haven't played TS2014, (and I'm not an expert in any stretch of the imagination) but from what I've seen, it looks pretty good. The graphics in TS are MUCH better, the graphics in Trainz vary between loco, rolling stock and individual pieces of terrain, which makes it look worse.
The actual gameplay from Trainz is okay, except for a few annoying problems (I switched from my loco (double ended (Class 37)) into a passenger car for a bit, switched back and suddenly I was in the wrong cab, 2 hours into a journey and I stupidly hadn't saved, I tried for a while to get back into the front cab but to no avail, this has happened quite often). There is a terrible lack of information on how to actually get this game to be playable in a simple manner, beyond the premade scenarios, and the tutorials are *alright*.
The optimization is HORRIBLE, now, I don't have that fantastic a computer, but I'm sure my 550ti and quad-core i5 should be able to handle a game from 2010/2011/2012 on it's lowest graphics, but I still get frame drops, even when I restrict myself to the cab view.
Overall... it falls flat on it's face in front of TS2014. The GUI and menus are HORRID, the game is very user unfriendly and just plain annoying. I give up. There is another Trainz game coming out, but I don't think I'll buy it if it continues down the current route.