Depends on what body type I would have. That's kind of what determines my choices overall. I'd love to be able to all kinds of things in regards to apparel, but I'm so limited in what will look good on my body.
Going on what I look like now, I would probably be a little fat and quite short for a guy, with a little bit of curve to my bum and hips. I'd give the general impression of being kinda round. So I suppose I'd dress in nice-fitting jeans and knit sweaters over a fitted t-shirt. Because that would suit me. Practicality and comfort.
However, if I had been born male I would probably be built more like my brother, who's six-foot tall with broad shoulders, longish legs and a solid, healthy weight no matter what he eats. If I looked like him I'd probably favor fitted dress shirts and either really nice jeans or dress pants. I'd probably accessorize more with that selection- scarves, watches, long coats, waistcoats, fun stuff. I'd do stuff with my hair and have a selection of glasses to match what I was wearing. I think that body type would be better suited to style and fun stuff than the alternative, though I definitely wouldn't sacrifice comfort.