If I can, I will say McGregor has more power, he will be much bigger. His foot movement will be faster than Floyd. Mayweather will be in his 40s, Conor in his Prime. McGregor will have ~3 inch reach advantage. Floyd gets caught early in fights and being rusty after not training specifically for a year will be a detriment. Conor is training considerably more often.
If I were to offer a hedge bet, Conor by KO inside 5 straddled against Mayweather by decision. Basically, I'm thinking Conor may be able to catch him with his blitz within the first few rounds. If it doesn't happen, Mayweather will win a convincing decision.