Flight. Reason, I'm on a roadtrip with my family and I look out the window and see valleys filled with trees and mountains immeasurably tall and all I'm thinking about is flying above ... that and I hate to travel. I have a terrible fear of heights but I think the shear awesomeness of flying would overcome that.
I would choose flight all the way. Invisibility just offers too many bad temptations for me. Its like an invitation to commit crime etc. And i would never do that so it would be not very useful to me. Plus, somebody would eventually catch on.
I'd choose Invis. First of all, I almost always get in a situation where I run somewhere, turn a corner and try to will myself to go invisible. Then I end up running again but he's right ****ing there. Plus having flight, you would become an Area 51 project. Like dissecting a frog, cept it's you. I wouldn't use invis that much, cept to spy on the damn girl that I like. Come on, WHAT BOY WOULDN'T. One girl, what's so wrong with that? I understand a whole locker room, but w/e. Plus if you didn't become an Area 51 project, you'd probably get about 5 gamillion people busting down doors and windows. So yea, Invis.