This game finally gets a release date and a name change thanks to capcoms innovative method of making europeans think the game is not a sequel. Anyway, this game does not just contain the addon for MHF2 but is MHF2 with the addon, thus you can use this game to start a new character from scratch. MHFU provides a new array of monsters such as the naruga, 3 extra MH ranks and a totally new map (+some maps from MH for the PS2).
There are a lot of small updates such as the fact that your box now contains more space and all items stack to 99. Mining points and gathering points can no longer be used if you have gathered all there is from the point. On the whole this is a game worth buying especially if you have a friend with which to play with as this is not really a single player game.