If the weaknesses for vampires weren't in effect, then I'd pick that, but with those weaknesses (like not being able to go out in sunlight) I have to say no. Especially as I like going out in the sun, and my birthday is in the summer and I want to do V Festival for it this year, and I can't go to a music festival in the sun if I'm a vampire.
Werewolves seem okay, but it's not really that cool at the end of the day. Plus transformation would be painful no matter what way you look at it. And there's no getting around that, OP, you can't introduce rules like that which break all established werewolf lore and claim that transformation wouldn't hurt. It's your entire body changing into a massive wolf beast, for Offler's sake. The only upside would be the hot, hot werewolf sex with a female werewolf, and that's not enough to counter the problems. And yes, I did watch the latest episode of Being Human to come up with the sex comment.
Being a goat? Aside from the mystical power to defy gravity on steep hills, there is absolutely nothing of benefit about being a goat. Except perhaps saving money on milk and cheese. And maybe being adored by Harry Potter fangirls who have a weird love for Aberforth Dumbledore.
No, I'd have to go for being a wizard. Using magic I can do almost all the cool awesome stuff that the other options have, and I could turn into an animal anyway so if I wanted to be a goat, I could be (not that I'd choose to turn into a goat, I'd much rather be a cat or a bird of some kind). Plus I'd have much more, awesome, powers to boot. I could make love spells to attract the girls, and hex my enemies, and use memory charms to never fail an exam again. Being a wizard would be so much better than the other choices. So I'd be a wizard.