When they fought Basilio was 29 and 30. Robinson was 35 and 36 ,prime for prime, there would have been no need for a rematch.
From what I have seen of Basilio at welterweight and the little I have seen of Robinson at welterweight I think the fight goes the distance with Robinson clearly the winner. Basillio did not have the power to stop Robinson or really buzz him. He would try to get in his chest which would be risky enough without the strength of Lamotta. I think Robinson has some edgy rounds there where Basillio is turning it on and bringing it. Those rounds would be close. However....when Robinson decides to get agressive too and throw welterweight Robinson leather....I see those rounds being clear Robinson rounds and very damaging to a face first tough guy like Carmen. Clear win on points: Robinson
A prime Robinson wins by a canter. Basilio would still have been tough enough to go the distance,though. Ray probably takes something like ten rounds out of fifteen on the cards.
More competitive than close. No need for a rematch, though fan fare and the nature of their fights might've seen to one. Fullmer and Basilio were rough customers all their own, but a good amount of the difficulty Robinson had with them was as much to do with the difference of age, mileage and wear and tear he had by comparison. I don't know if that's nearly as applicable in regards to Turpin, who was both awkward and physically imposing. That was one hell of a win in 1951: The only man to beat him officially prior to his first retirement without holding a significant weight advantage (obviously LaMotta '43, Maxim '52).
Middleweight Robinson leather was more deadly IMO. Of course, I'm basing that on having actually seen most of his MW material and his more impressive list of stoppage wins at the weight than he had at 147. I think his power saw an increase when he put some bulk on his frame, even if he'd declined in several other areas.
Robinson was what 36/37 for those fights, in a long career taking punishment, without nutritional supplements or PEDs that's pretty old. I think Prime Robinson throws more and moves more to win convincingly
Robinson would have or at least should have won pretty easily. Other than Gavlian who would have been better than Basilio, that Robinson fought at 147?
Probably Armstrong had they fought a couple years earlier, though he'd been on a nice roll at the time. Possibly Fritzie Zivic, whom Robinson took the #1 rating at 147 from in only his second year as pro. Basilio against either one of those guys would've been an exhibition in brutality too. The only guys who could've possibly been tougher or better than Gavilan though are SRL and Hearns. Burley?
I think it'd have been very close again. Basilio wasn't exactly a big welterweight, let alone middleweight. At 5'11-6' with a big frame, Robinson was a large welterweight and decent sized middleweight. I think the fights would've resembled their middleweight encounters, but with more fireworks.