Will all due respect to Tunney I'd have to go with Johnson on this one. Johnson was the bigger man and he could move very well. Gene Tunney had trouble with Harry Greb I believe is because of Greb's footwork and pressure. I can see Johnson as giving him a lot of trouble with his footwork. Besides Johnson was hard to hit, could feint and was often the bigger man in his fights, and he would be so in a fight with Tunney.