Despite his ill-fated attempt to catch the ball with his crotch in this year's NLDS, Matt Holliday is superior to Jason Bay defensively. You wouldn't evaluate a player's batting skills based on 1 plate appearance and you shouldn't judge a player's defense based on 1 misplay. I've seen the Bay > Holliday myth propagated in a number of places so it's worth addressing. Here are each player's UZR and +/- (in runs saved) for the last 3 seasons combined:
Additionally, Holliday rated higher than Bay according to the Fans Scouting Report this season. The extent to which Bay sucks defensively is up for debate but it's pretty clear he is below average while Holliday is above average. The end.