Depends on the day, depends on my mood. Depends on the dude. I'll say oral just because it's consistently great. Only once, or twice, has someone been too rough and left me with bite marks. And when someone chooses to swallow? Oh, man... How I get off on that.
However, with anal (when I've bottomed), it's hurt more than once or twice. Mainly because of a lack of lube, or a guy being really thick, but these days I'm almost exclusively top, however, I still think about bottoming sometimes. Mostly because there have been two or three times where bottoming was pure bliss and heaven on earth. No joke. I did not want it to stop, and I kept yelling, "harder." Two of those times made me come hands free, too.