The first contravenes PBP 45 ("Don't use barewords."), but behavior-wise as long as it's a plain bareword there should be no difference.

Stylistically though it'll get you disapproving glares from the purists (granted I still violate 45 myself out of old habits; working with Ruby is slowly changing that (although too much Rails makes me tend to try $hash{ :key } instead . . . )).