Floyd Patterson vs. Gene Tunney ?

Harry Greb (the greatest Middleweight Boxer of all times on many expert lists) was the only man to beat a prime Tunney - and was by all description (even though we don't have film footage) an insane, dynamic swarmer that came at you from crazy angles. Greb had a jack in the box energy to his feet when in his prime, but lost to Tunney when he was past his prime.

Patterson was also a swarmer (of the Cus D'Amato school). Tunney knew how to fight swarmers (look at what he did to Jack Dempsey - a bigger puncher than Patterson and also a swarmer).

I say Gene Tunney takes it by substantial UD.

Tunney was an excellent boxer, but Patterson was too and could hit with very fast combinations. Both about the same height, but Tunney would be 10 pounds lighter and be moving all over the ring .Still like Tunney in this one.

Gene Tunney wins easy

I am going with Tunney who had enough power to hurt Patterson.

Patterson was a small heavyweight who used speed to win but lost to heavy hitters.