i have both. i wear glasses in teh morning when i wake up, and then i put on contacts.
i used to just wear my glasses, but i never liked how i looked in them. then, i got contacts, and wore them for a year, and then I was like "meh, its kind of a pain in the ass to put these in every morning", so i went back to my glasses. then, over the summer, i broke my glasses, so they look ridiculous, so i only wear them when i'm alone when i wake up.