Tua is made for any version of pre prison Tyson, barring maybe the Douglas version who was out of shape and probably high as hell. The speed, power, and footwork are just too dynamic a package for Tua to handle. I think Mike within 7 rounds is about right.
Both have great power and chin. Both are pressure fighters. The difference is Mike fights like a kid whose bike got stolen. David fights like a kid whose bike got stolen but he didn't care for that bike in the first place.
I think Tua goes into a shell a little bit like he did vs Lewis and is happy to see it out. Fight probably degenerates into a sort of wrestle-fest.
In all honesty, I think if Tua couldn't find a guy he'd just give up or rely on his power to bail him out of a points deficit. He wouldn't have to look for Mike (in the sense that Tyson would always be on him, not because Tyson is bad defensively). He gives it a real go but Tyson is just far too skilled, fast and accurate. I reckon a stoppage around 7.
Tua would be beaten up badly by a prime Tyson. Too much speed, power and dimension that will make Tua be too gun shy to pull the trigger or land a Hail Mary.
Tyson was just much better. Faster of hand and foot (although Tua had nice hand speed in his youth), a more wide variety of shots. The guys who troubled Tyson the most did so with uppercuts, jabs, straight right hands, and picking the right mix of movement and clinching (where Tyson was lazy). Tua was too reliant on the left hook. Tua could take a good shot, and would be more cautious when he took harder shots, so it might go the distance. Or maybe Tyson just lands too much and stops him in the mid rounds