If nothing else about me changed and you take out the transition period/problems, I'd pick MTF. No disempowering female socialization holding me back from being and doing what I wanted. (As others said, no periods, no pregnancy fears, no being dogged by constant fear of rape.)
I could deal with being an old bat after all that. Men don't find me attractive? Bring it on! Getting stared at, touched, and harassed by randos in public sucked! And old ladies do get respect in certain situations, more so than young women. Oh, and don't forget all the mind trips about sex young females are subjected to. Old bats are assumed to be "experienced". Plus, healthwise, old lady trumps old man any day of the week. Only problem would be having to give up being a guy. I am the sort who likes my dessert last. Problem is, dinner made me sick to my stomach, hard to enjoy anything after that.