Floyd has less power P4P, but he has better defense and a much better chin.
Floyd takes this easily on points or stops Rigo late. Rigo is just too passive with his offense and isn't nearly as versatile in that area.
Floyd struggled with Judah's speedy southpaw style and Rigo is slicker, faster and hits way harder than Judah plus hes more mobile cause he has the best footwork and foot balance today.
However Rigo does have a weakness that people seem to ignore, he has a useless right hand. When he paws with his right jab or slaps with his right hook, which he does often, it makes him very susceptible to the left hook. Also hes not as well rounded as Floyd cause I dont think he can fight in close range
This one is too tough to call, gun to my head I think Rigo's left hand will cause so much trouble for Floyd especially since in your scenario neither has a size or reach advantage and Rigo has been exclusively fighting much bigger fighters
Floyd would win. He has so much more options than Rigondeux. Rigo keeps his gameplan farely simple and he is really damn good at it, but Floyd would switch it up against Rigo and possibly stop him late.
Ranged against better competition, Rigo sheds his beast image and retreats to a defensive phalanx which only works against average boxers and mindless brawlers. Having the longer reach, more mobile and versatile, Floyd I think would content on pot shooting his way to wide points win.
Probably Floyd Mayweather by a close decision. Even though this would be the most boring fight of all time, it would bring in huge money.
Who wins . Ignoring weight classes. 147 pound Floyd vs 122 Rigo