I use a 92mm fan, but that's just me. I would think it would be better because of the increase in air flow, and if the dead zone is the same size then I can't see how a 80mm fan would be any better. How do the speeds compare?
I'd go with the one that delivers the higher CFM, so long as the noise was tolerable. Dead zone may be a worry, though, if the central hub of the 92mm fan is bigger than that of the 80mm hub.