I think it's pretty clear that Hammer was better this year than HRod and that Hammer could have helped us more this year. If he was playing left field for us and Morse was playing 1B for us all year, we'd probably have a better record than we do now.
With that being said, Hammer may have gotten us maybe 3 more games? In the greater scheme of things, that's not a lot. And then he would have been gone. HRod could help us out for the next several years.
Also - going into the year, I would have been pretty apprehensive if we were relying on Hammer to play 130+ games in LF and Morse to have the kind of year he actually did have this year.