Two things jump out at me here. First off, Generations is only $6.79. That's a pretty good deal (or at least it is in the world of sims expansions). It's as cheap as the stuff packs anyway. If you don't already have Generations, and you'd like to pick up at least one expansion pack, that's the obvious first choice.
Second thing, Showtime Katy Perry CE is the same price as the regular version of Showtime. I would never in a million years pay so much as a penny more for the stupid Katy Perry version. But if they're the same price, why not?