Yeah difference between best and greatest. Robinsons fundamental style was great for his time but for right now styles have evolved. Mayweather may be better in terms of what his style brings and the speed and power with it. But that in no way means he is greater then Robinson. Just better in terms of his advantages with time, and boxing for over 50 years ago I would expect its possible to be better then a fighter was 50 years ago as the sport has advanced. Doesn't make him "greater" though.