There are some differences between this game and the PS3 version:
-You can't get any DLC
-The graphics aren't as good (obviously)
-Not nearly as much traffic
-Only up to 4 players online rather than 8.
The core game, however, is exactly the same, just made to work on the PS Vita.
This game is definetly worth the price. Just note that there is no local multiplayer of any sort. It's all online.