As of now I would have Mayweather winning against any version of Mosley, I don't think any version of Mosley would be particularly easy for Mayweather to beat even if he in a boxing sense outboxed Mosley quite dramatically I think it would be a competitive fight, like his fight against Oscar. Even though he landed twice as many punches he simply doesn't have the physical presence at 147 to really impact these guys enough to make it a totally outsided affair.

That being said I can't really determine how these two would have matched up until we see them fighting in May, that will be a good oppertunity to get a barring of how Mayweather would have fared against a younger Mosley. IMO Mosley has changed his style a lot less dramatically than Oscar did... at least as a welterweight.