Tua. Common opponents : Maskaev , Jeff Wooden , Monte Barrett , Lennox Lewis , Obed Sullivan , John Ruiz . Of those Rahman stopped Wooden , Lewis , and Tua didn't. Tua stopped Maskaev , Sullivan and Ruiz , and Rahman didn't. 3:2 for Tua. Also Rahman managed to KO Lewis and Tua didn't due to height differentials which prefered Rahman , maybe same for the Wooden case. Also , having watched both , I say Tua is the more formidable puncher . Actually he is the most formidable puncher for anyone reachable for him which explains Lewis .