The fight could go either way in my opinion.
If Randy can impose his will, I give it to Randy hands down. I don't see Wandy having nearly the KO power that Chuck has. Sure his ground and pound is the best in the game IMO, however, I don't see Wandy being able to get him there. I think Randy could take him down pretty easily and do what he did to Tito and Chuck (well the first time anyways).
If Wandy can effectively strike and take Randy down, Couture would be in serious trouble. If Randy also isn't in tip top shape Wandy could take him out.
I'd give it to Randy but that's just me.
"Hang The Dj"