For much of the same reasons I'd take Miller over Fleury is why I would take Howard over Fleury.
Pittsburgh is a good team, and should be able to make the playoffs easily, with that said they probably won't be to inclined to put Fleury in the net as much as usual, add that to the fact that they have a more than servicable back up in Vokoun, Fleury should take a hit in games played and thus wins.
While Howard and the Red Wings are going to be worse off without Lidstrom, the team is going to need Howard more than ever. The Red Wings are going to be in tough to make the playoffs this year, with that said they are going to look to Howard giving him a shot at more wins than Fleury.
In short I think there will be a significant difference in games played, to warrant picking Howard over Fleury.