I just started with Touchgrind Skate 2 after only playing True Skate for a year (I didn't play the original Touchgrind). I jacked up my account and got annoyed with True Skate because of user error, so I figured now was as good a time as any to switch camps.
While they do play really different, I am finding that with Touchgrind I know what tricks are going to happen when I do them. My gameplay in True Skate was basically mad swiping, hoping that something awesome would happen. Missions were a nightmare because I can never figure out how to be as precise as the model.
With Touchgrind, I feel like I'm learning how the tricks actually work in real life, and that is making it get a lot easier to control a lot faster. (I have no skateboarding background.) I also like the vibrant colors and overall "game-ness" better. I'm a sucker for challenges and unlockables, so this is scratching that itch better than True Skate was.
That being said, I really enjoyed True Skate (I'm an either/or kind of guy, so I deleted it). I loved being able to play with only my thumb. And the skateparks had solid variety. I've only played in the Backyard so far on Touchgrind, but I have finished all the training and challenges there.
At the very least, my day one impression is very positive. Even with having to throw out everything I know about controlling a digital skateboard, I still like it a lot.