I guess it depends on the guy for me. I don't normally like a mustache with no beard. I'm not sure why.
My previous boyfriend (not my current ex but the guy before him) had a mustache and beard. He actually looked kinda funny without them. Then I met my current ex, who was all of 22 at the time and not very hairy on the face at all. I got used to the clean-shaven look, although I really liked the stubble once it grew to a certain length. A little shorter or longer, and I didn't like it.
On me, of course, I'll take what I can get. I have a mustache, but it's so flimsy!