I don't really have a problem with either. I've probably got something close to a 50/50 split of girl/guy friends. Maybe 60-40 slanting towards girls. But my roommate is a guy, and another guy lived here for a few months that I'm friends with. Neither of them made me uncomfortable.
Uncomfortable people make me uncomfortable, regardless of gender. So I don't really have a preference. I will say I have closer female friends than guy friends. Like if of my top 5 friends, the top 3 are women. But I know some really wonderful to be around guys. So whateva.