I think Tyson in his prime packed more power in a single punch than Lewis did, but over the course of a longer fight, Lennox had more cumulative strength. If a fighter made it past the 6th or 7th round against Tyson, he had a good chance of going the distance or even beating him. Surviving the early rounds against Lewis however, would not necessarily guarantee safe passage. He had a different kind of strength and power that could finish you off late.
No, not really. Lewis had only two stoppages past the seventh round in his career, and those were both in the eighth round(Jackson and Tyson). Tyson had one(Ribalta in the 10th). Not really much to choose from there.