I'd go with Pryor. He had more speed, unlike Armstrong threw in combination and had stamina to match Armstrong with. He also used the jab to set his work up. So he should outbox Armstrong.
Awesome fight, Hammerin' Hank ends up forcing Pryor back and after 7/8 vicious rounds, Pryor is beaten into submission. Pryor may be the quicker guy, and may throw more, but in a brawl you tend to favour the guy with the better chin, and Hank had decent pop around 140 too.