I have done a lot of testing on this actually...
Domination is only about 5-10,000 XP on average, and this is getting 30+ kills a game.
Search and Destroy average is 15,000-25,000 XP a game with only 5-10 kills a game.
So search and destroy is by far the best to rank up if your decent and can get kills or plant, also you'll notice the players in S&
are a higher prestige then any other game mode.