Looking at the Star Wars movies in a completely neutral and objective way, I honestly can't see so much "evil" about the Sith and "good" about the Jedi. The Sith try to eliminate the Jedi, yes, but vice versa as well. And good things can be done with the so-called "dark" side of the force, ie. Anakin's wife (albeit, he screwed that one up)
That said, I'd probably be a Sith. It's the faster route to power, and as long as I keep the power in check I'd use it for things I deem to be good.
Protip: NO ONE thinks of -themselves- as evil. Everyone believes they're helping the world, even if they're horribly misguided.