I'm versatile and consider myself to be equally good at both. Because of my dick and body size, I end up topping more. Also, more picky about tops. Being 6'1 and a solid 220, I can't ever bring myself to let thin guys that I outweigh my 70 pounds to top me. Go figure that they have the biggest dicks. I take versatile to mean "either way" or "up to you".
Anyway, for me it depends on the guy/who's cleaned out/chemistry. In my experience, who's doing what was already established before meeting up. I'd love to flip but most guys can't do both in one session (including me). If you get fucked right, you're dick is often limp after. Sometimes I have an exception and cock rings really help. But yah.