TMUF had much more variation in building tracks, because of 7 different envis. Although I really like to build Canyon maps. The TM²-Editor is much more comfortable, because of the copy/paste-tool (I remember deleting and rebuilding maps in TMUF several times, because I reached the limit of the building space somewhere).
Also there are now much more possibilities in the Mediatracker (though they screwed 2d-triangles up) and especially the idea of the GP roads is nice, because they are not centered, but either more on the left or on the right side, which gives some cool new possibilities.
In my opinion the editor itself got much easier to handle in TM2, it's also easier to build some quite cool tracks and the MT as some nice new features, but Canyon as an environment itself as advantages and disadvantages as well as every other environment. Though I have to admit it's much more approachable than the most TMUF-envis, because you aren't this dependent on transitions and smothness anymore. In TMUF the cars easily lost control on unsmooth spots, Canyon is much more beginner friendly in this aspect.