One of the tougher fights for Louis among all of the HW's, but I have to go with Joe via decision or KO. I would say decision due to Holmes' greatness, but Louis in his prime KO'd just about absolutely everyone (Farr and a few others aside) so it's tough to say...
Louis never in his life dreamed of seeing a fighter with the skill of Larry Holmes. Larry Holmes cuts his ass. No contest.
I don't want to get in a pissing contest but Holmes only a couple times ever fought the caliber of opponent Louis had many many times.
Holmes in his prime had a great chin, well, he can get dropped but he can bounce back the way he did against Shavers. Louis would have his moments and probably drop Holmes but he'll lose more rounds by getting out finnesed and out jabbed. Remember, Louis is not that very good against movers, and Holmes is no slouch with his footwork.
Holmes is faster, faster on feet, greater on his feet, great skill, enough power to keep Louis tame, "ok" jab.
Very few people have him rated 1-3 and he deserves to be there. Probably the toughest match up for most heavyweights.