Which Sims3 game should i buy?

okay, for all you simmers out there you know that Sims3 Generations came out today. well, i have 40 dollars, and i wanted to go get it. but i only have Sims3 and Sims3 World Adventures.World Adventures got boring to me because after you do all the missions that's it. you get a new family and its the same missions over and over again. so do you guys have any advice on which game i should get? i really want Night Life too, but i can only get one.