I'll give you a hint: This wouldn't be a Chessmatch. I'd have to think that Armstrong's better infighting abilities and offensive subtelities give him the edge.
I think Pryor might actually start off trying to box Armstrong (and might have some success early), but Hank would eventually close the gap and outfight him at close quarters.
Yeah, I think Armstrong's strength is the decider. Pryor is one of the few I've seen who's both faster, and throws more than Armstrong, but I can't see him doing so well while fighting off the back-foot. Armstrong would absolutely put him there.