I started at roleplay as just female because of it being my own gender, but as I started doing yaoi I roleplayed as a male. Then I got into a lot of roleplays and decided to try out playing male. When it's my own plot, I love rping as a male or sometimes, I volunteer to play the male witha specific pairing because they tend to be my favourite characters.
Now, honestly, I don't think I have much of a preferance. As long as I play female sometimes, then I don't mind either and might actually like playing male more.