Which Sims 3 Expansion Pack should I get?

[Sammi]

Out of those two I suggest generations.
Ambitions is fun because it comes with a new town, and new skills like sculpting, and new professions like investigator, interior designer, salon stylist.
And Generations is mostly like new furniture and clothing, [no new town]. It's lets you customize your sims to be more realistic in a way, like family life. There's also video cameras that you can use to record you sims life and then play it back on the tv. And actual weddings, bachelor/bachelorette parties. Teens can have there parents go away and have teen parties, graduate from high school. There are also boarding schools for teens and children that teach them skills depending on which school they go to.

In summary, Ambitions is like new town, more skills, more jobs called professions [where you actually do the work rather than send them to a building and set the speed on fast]
And Generations is more clothing, furniture, interactions to make the life more realistic-like.

Whatever you choose, they are both good games!