Gunn beyond a shadow of a doubt, based on what we saw of the two men fighting.
Look at the fights that Wood was involved in. The one in the alley, he took out one vampire. The next time we see him fight, again against a single vampire, Spike has keep him from being a happy meal on legs. The third time is his one on one against a thoroughly distracted Spike. If he had kept his mind on business, instead of gloating like an amateur, he might have gotten the job done, but once the trigger is deactivated, Spike makes toast out of him without half trying. Then, finally, in the big battle, if not for Giles, toast once more, which, granted, wasn't too hard to accept, considering the odds, but he was the only one in the entire group to almost immediately lose their primary weapon and have to fall back on a puny little 2 1/2 inch push dagger.
Gunn, on the other hand, goes about the business of taking out vampires and demons in a totally cool, controlled, professional manner. No gloating. Axe swings, vampires turn to dust. Even in his final fight in "Not Fade Away," when he faced off against a whole room full of vampires, he got the job done. Okay, he got pretty well chopped up in that one, but still, he left in one piece, and the bad guys were dust.
The way I see it:
Wood ain't no good,
But Gunn gets it done.