In the real world, I'd be a hero/villain, depending on who you asked. To Christians, I'd likely be the anti-Christ, for example. Palestinians would probably have a different opinion, depending on whether or not they could get over having an atheist lesbian telling the Israelis to back off. The real world is far too complicated to simply say "I'd be a hero/I'd be a villain." I'd do what I felt was right, and let people judge me on their own. If too many people didn't like what I felt was right, what do I care? I'm super strong and invulnerable. Suck it, peons.
In a comic book world, I'd go with Marvel. Mostly because that's what I always used to read. I'd probably sign up as a reserve Avenger, and otherwise go about my normal life. That way, when Really Bad Stuff(TM) is going down, I'll be there to help. But for day-to-day things, I'd leave it to the people who are out there every single day. Ending up with my own rogues gallery and people wanting to off me/my loved ones just doesn't sound like that much fun. At least in the real world, I'd have the advantage of being more powerful than they ever could be. In a comic world, not so much.