2D, as always. It's easier to see what's wrong with your team on the pitch. That, and i just can't stand to watch match in 3D, like someone else said, it's abomination!
3D, last year my PC was a **** and I had to use 3D at the minimum setting, this year I have a better PC and I can max out the quality without even stressing my PC. I can't believe how crappy 3D at minimum looks compared to 3D Max.
Also throw in the better pitch mod and the real advertisements mod and it looks great!