Toney fights more flat footed and inside. Floyd moves a lot more. Both are excellent defensive counterpunches, but their styles are different.
Toney was a better "fighter" out of his shell. By this I mean that he was better able to mix his defense and offense. Toney would bait people in , slip and counter. Floyd fights in modes. If you corner him, he goes into defense mode, slips, slips, slips some more and then escapes. After escaping, Floyd uses his offesnive mode to throw some pot-shots.
Floyd > Toney. Wer'e talking only one facet here, shoulder roll, and Floyd's = to Toney in that respect. He is a much better fighter in the other facets of the game
Toney could get away with standing in one spot and relying soley on the shoulder roll, where as Floyd uses all the tools in the shed to get the same job accomplished. I think Toney is just a tad to lazy and arrogant, doesn't think he has to move. Mayweather is a tad smarter and realizes he serves a better chance floating around the ring.
Because that's the way he was taught by Bill Miller. Toney was weaned on old tapes of Archie Moore and Ezzard Charles and the stand in the pocket/roll, slip, counter style is a great minimalist, energy conserving way to fight, if you can master it. This style was good for Toney at the lower weights because he was often weight drained and could effectively increase his stamina with limited, subtle movement. The other great thing about Toney is that he was almost in position to punch with power after making the other guy miss. You keep your base under you when you roll a shot. You're on balance and ready to whip the counter right hand in and work off of it. That's what Toney did like a master. Floyd's shoulder roll is different. His slipping comes more off of movement and footwork, and his counters tend to be more flurries than sharp single shots, because his feet aren't always set after the slip. PBF is just so damn fast that he can sting you without having to be set, then oftentimes either turn out or move away at an angle before you can even think about countering his combos. Completely different styles, really.