Whitaker by a country mile. Spence is still young enough to get better, but for now he has a lot of bad habits that would get him badly beaten up against Whitaker. That super wide stance that Spence has that exposes his body wouldn’t get him very far against a top notch technician like Whitaker. Spence also still hasn’t learned to pace himself well and over uses the high guard.
I rate Spence (and Crawford) really highly and pick them to beat a few great/very good fighters from previous eras, but I think Whittaker (upto 1996) takes care of business. A competitive UD against Spence
Whitaker would have more composure than Spence and pick him apart. Spence does not impress me, you know, om a macro level.
Why not 15 rounds like all title fights should be? Over 15 Whitaker turns it into a romp...even more lopsided.