I picked up both games yesterday and I'm happy to report that we have 2 good hockey games this year!
2k7
2k is the culmination of 5 years of work. The presentation is the games weakest point. The new camera angle is nice but the cinemotion with music is only worthy of playing once in a while. The commentary is barely average and nothing new from last years game. Pretty much the presentation was cut and paste.
The graphics offer mixed results. The cutscenes and intro stuff look like ass compared to NHL 07. The players are way too skinny, especially the goalies, and they just don't look right. Fortunately the chainmail jerseys from last years game are gone.

The action on-ice looks great though. The animations are fluid and the framerate is fantastic. The players even look better in-game.
Out of the box this game needs major slider tweakage. I found myself completely disabling the speed burst because I liked that from NHL 07 so much. I had to drop the speed of the game way down as well. If you've played 2k hockey you've played this game (that's not a bad thing unless it's growing old for you). It plays identically to the version they released last season. The only differences are some slight graphical touches (no more chainmail jerseys), an excellent new skating model, and the cinemotion camera angle and music. Crease control returns and is a fun little diversion in small stretches.
Bottom line: If you eat, drink, and sleep 2k hockey you'll love this title. If you are growing tired of the same engine give NHL 07 a try.
NHL 07
NHL 07, IMO, is a breath of fresh air in hockey videogames. The new controls translate very well to gameplay (of course that won't be the case for everyone) and it is a complete blast to play.
The presentation in this game is top notch. The commentary from Thorne and Clement is excellent and the cutscenes between plays are jaw-dropping. The default camera angle is solid. The goalie animations are unmatched but the skating animations are not as smooth as 2k's.
The graphics in this game are stellar. The cutscenes, as mentioned, are jaw-dropping and the in-game graphics are adequate. The framerate does not compare to 2k's but it is not so bad that it detracts from the gameplay.
The game plays better out of the box than 2k does. I haven't touched a slider other than game speed and I've been seeing a lot of cool things happen. The new analog controls really open up the offensive play and options. Playing defense isn't nearly as much fun but it's not bad. The puck physics are nicely done. I've seen some pretty awesome things happen with the puck in my limited time with the game. Passes go offline as do shots. I was able to play a game with Jimmy online last night and it was immensely fun online. I think that's where this game shines the most. Playing against a human opponent really changes the feeling of the game and it really does feel very sim-like.
Bottom line: If you're a total die-hard 2k fan you'll likely think this game is pretty cool but you'll want to go back to your 2k. If you're looking for something fresh and new in a hockey game you owe it to yourself to try this game.
My initial feelings after playing both games last night is that I like NHL 07 more at the moment. I think a lot of that has to do with 2k being largely the same and 07 trying something different. 07 makes you unlearn how you've played videogame hockey for years and to some that will be a major turnoff. For me, it's a major turn-on.
I am a patient boy.
I wait, I wait, I wait, I wait.
My time is water down a drain.