Tyson. I always felt Pryor was overrated in terms of "greatness". He was a great h2h fighter but so was Tyson. Tyson accomplished more so I go with Tyson (greater). Tyson was also better.
It's amazing that a bum like Pryor, a 5-6 lightweight could put Sugar Ray Leonard down when they sparred. Yet he was ducking Johnny Bumphous.