To call Floyd chinny is pretty absurd to be honest. Granted, he has the best defense in boxing, but he takes the odd flush shot, and he takes them fine. His chin is solid, above average at least.
Mayweather's chin is alright. I don't see any reason to call him chinny but I also don't see much of a reason to think he has a great chin. Shane rarely hurts guys early on but he hurt Floyd with that 2nd right hand (around the temple). Floyd's never been SERIOUSLY hurt, he's been buzzed and a little hurt, but not badly hurt IMO. I'd rate his chin a 7/10. It's difficult to assess since he doesn't get hit flush very often
Ortiz wasn't ready for the fight then. Even still he was beating the empanadas out of that kid. He's stronger at welter and maidana would only be worse in that division