As Shoe said, the developers are in completely separate leagues. However, there isn't really much contest looking purely from the perspective of who can make a better Halo game either. To be fair, 343 has far less experience as a developer. The fact remains that Halo 4 was a huge departure from what made the earlier games in the series work so well: the fact that they were, at heart, competitive games. While I commend 343 for tackling one of the most beloved franchises in gaming as a new developer and doing an incredible job with the art and sound design of the game, I am also hugely disappointed with just how poorly the game's multiplayer sandbox was designed. Halo games have shipped with less polish than Halo 4, and Reach had its fair share of poor design choices, but nothing comes close to just how inherently broken or poorly implemented most of the new game elements introduced in Halo 4 were.
In short, I have respect for 343 in some ways. However, their design philosophies need a lot of work if they want to develop a Halo game that can show its face alongside games like Halo 2 and 3. The company has some serious talent in some areas, but is woefully lacking in direction in the Sandbox design and Multiplayer departments. Again, i don't think it's fair to compare a developer with multiple beloved franchises to its name to a developer who has put out one game. That said, by that comparison there is really no contest at this point. Only time will tell what 343i is capable of in the future, but they need to seriously reevaluate some of their design philosophies if they want to develop a competitive FPS of any quality.