Nightwing all the way. Unless Red Skull has suddenly gained a massive upgrade in skills or powers (which he doesn't have to my information)...from what I have seen from Skull, the fight would go like this: http://img456.imageshack.us/img456/...facethrough.gif
Yes, he has the cloned body of Captain America, but what good does it do if he doesn't have skills to go with them? Nightwing isn't that far from Captain anyway. He is truly underrated when it comes to stuff like strength, for example.
I think nightwing will win it as well, but Im not sure if it will be that easy. red Skull has beaten cap before and has almost beaten Black Panther up, and would have if BP didn't get some help from falcon....................