I would choose invisibility, because I believe it offers more chances for good, evil, privacy, and just plain fun. I would want to keep my invisibility as big of a secret as possible; I wouldn't want to be known for my power, so I'd have to be careful when going into and out of invisibility.
Here's some example scenarios I thought up:
Fun:
- Messing with people's minds (which some may consider evil). For example, making them think their house is haunted. Slam doors, move furniture, flip switches, unplug stuff, etc.
- Instigate confrontations (may also be considered evil). Make someone think they shoved them, hit them, etc.
- Going into restricted areas just to see what's there.
- Listening to what people have to say about me when I'm not there (may end up being depressing...)
- People-watching for hours without looking creepy or suspicious
- Just doing normal things while invisible. See people's reactions while you drive a car, ride a bike, etc., while invisible. Doing that too often may draw too much attention to myself, though.
Good:
- Infiltrating terrorist cells; I'd be able to gain information relatively safely, maybe find Osama?
- Security. I can scream and throw shit to scare the hell out of people from stealing stuff.
- Crime-fighting. This is a toughie to imagine scenarios where an invisible man would stop crime, especially if you want to remain unknown. News reports about an invisible person fighting crime would definitely not be something I'm looking for. I'd probably have to learn some martial arts so I can actually kick some ass, and bulk up some. And it's not like you can dodge bullets; if criminals caught on and were aware of your presence, they would just pray-and-spray all over the place, and you'd be sure to get hit at some point. If the criminals aren't armed with firearms, then it could be easier.
Evil:
- Stealing stuff. Assuming that if I'm able to fit an object into my pocket or under a shirt/jacket, it will become invisibile, then it's fair game.
- Infiltrating governments, agencies, etc. for classified information. Maybe it will be considered good if I give the information to Wikileaks? :P
- Murder, or any extreme crimes. Any eyewitnesses would be completely baffled.
Miscellaneous thoughts:
- Useful for if you are trying to avoid someone, or conversely, if someone is trying to avoid you.
- If you've ever wanted to just disappear from the world for a little bit, you got it!
- I'd assume that while invisible, you don't just pass through someone or something, you still have to walk around it. So it would be annoying to constantly avoid people and objects while you walk around, especially if you're trying to be secretive about your power, or not alert people to your presence. No chance for clumsiness!
- It's always best to have a complimentary power, like super-strength. Just one superpower doesn't always cut it, especially for fighting crime.
That's all I'll put, it's getting too long.