Both are good...
2K7 has a feature called Cinemotion, which plays orchestral music according to what is going on in the game, I know, it sounds corny, but it's like watching a movie sometimes, is really cool.
NHL 07 uses the L stick for player movement, and the R stick for moving the stick, you do your passes and shots, and dekes and all that. It has a few bugs and kinks to work out, but it is a good game.
Try the demos, and figure out which one you like better.