I would choose to fly. Then I would drop purple paint on the world so all the invisible people would appear.
If you can fly people are going to stare at you all the time and when you land they'll follow you around and be all "how'd you do that?" Which would be really irritating. So I'd say invisible. But people will notice when things just start floating away so I'd want to be able to make other stuff invisible too. But then I might put it down and not be able to find it. This question is too hard.
If you don't like heights, chances are it's because you're too conscious of the danger of falling. If you could fly, there would be no danger. It would be the same as how you don't fear 600-foot-deep water if you can swim in 6-foot-deep water! Trust me when I tell you that you can get used to heights -- and you especially would if you could FLY! I know because I skydive, and when you begin skydiving, you are pretty afraid of that open door on the airplane! You are forced to get near it before getting out, and you get to look down at the ground 13,500 feet below!! It's FREAKY! But then you get used to it, and part of that is realizing that you have two parachutes to protect you from the danger that the door represents. From then on, it's pure fun! So obviously, I would prefer to be invisible. No... wait... I mean, I'd like to be able to fly! LOL! I love the sky, and I love to be in it. -Jeffrey