Wow. Brings back a lot of memories. I wrestled for 2 years and ran for a lot more than that. I gotta go with wrestling in terms of disclipline, cutting weight, mental toughness, all around agility and athletic ability.
Racing competitively is no picnic, but there is simply nowhere to hide on the mat mano y mano. In an xc race you can slip into the pack and claim you just did not have your best stuff on that particular day. On the track, there are usually other competitors you will beat even when performing poorly. On the mat, you are 100% exposed if you don't give it all you got. Yeah, wrestling gets the nod here.
Oh and one more thing, don't ever fight a guy who knows how to wrestle. It will not end well for you.