Joy seems a very simple name to me - not at all frilly. Also, people with certain kinds of depression experience all their emotions very intensely - including the ones we think of as 'good', such as joy. So I don't see the problem there, any more than calling a son - who could turn out to be a bit of a loser - '
Victor'.
I'll admit I don't like the sound of
Joy all that much, but of the two I'd pick it
Joyce I actually hate. I don't like the juicy sound of it. For a female it seems fancified, along the lines of adding an 'e' to single syllable names just to be really sure they're feminine enough. And even so,
Joyce is more a male name to me
http://www.behindthename.com/pnl/167578