I think Rev has an easier time coming in on Gallade than the other way around. Gallades runs Close Combat as its fighting move of chocie so if it gets a KO with it, it gets a defense drop on an already dismal defense, easy target for Rev, the problem gets even worse if its a life orb user.
Alternativly, Rev normally scores KOs with a few bulk ups on its belt and hammer arm, but the speed drop isnt going to hurt it against Glallade when its got Shadow Sneak. Plus with Leftovers as item of choice along with shed/rest, it will also probably be near full health against it as well. I think they look a lot close on paper than they do in practice.