I say wear whatever it is that you think is comfortable and prefer.
If you're going to, the point is to have fun, correct? If you'll be able to be more comfortable in a certain outfit, the chances are you're going to end up having more fun, as you won't be worrying the whole time about your top.
Also, I just wanted to say, that your friends probably won't jump the gun and believe that you are just saying trans for the attention simply because you choose to wear a certain outfit over another. I'm sure they're all aware that everybody has their own opinion when it comes to clothing.
Plus, if they are truly real friends, they'll have already accepted your word for it without question.
Go in what you want, that's what I think you should do, at least ~