I would give it to Marquez. The way he adapts in the ring is brilliant, Marquez/Pac 1 being a great example. He doesn't just "recover" but makes the necessary adjustments mid fight if he has to. His preparation for a fight is also great and I think him and Nacho do an excellent job at studying their opponent and coming in with a gameplan. As for Mayweather, I think his success has been due more to his skill than to his ring IQ. Not taking anything away from it, he's definitely up there in ring smarts, but I think its more apparent in Marquez. Also, I think Mayweather is actually pretty smart outside the ring. He knows alot of people hate him and he uses that to his advantage. He plays the villain role well and its what gets him so much attention.
There both smart and adept at their own styles. Juan is a pure boxer, and great tactician/ combination puncher . Floyd is also a great tactician although he's relied and had the benefit of amazing athletic gifts. I'd say their about even IQ wise, maybe with an edge to Floyd, but I don't think Floyd dominating Marquez has any bearing on this, consdering Floyd had every physical advantage in that fight and mainly used his speed and athleticsm to beat Marquez not his IQ.
Floyd but probably not as big of a gap as people think because floyd has physical advantages that JMM doesnt. You'd have to ask if JMM ever struggled due to making bad decisions or strategies in the ring. Like say getting dropped by Pac 3 times in 1 round, that wasnt really due to an error in thinking, Pac just got him with his speed and he was dazed still so got hit again. If he had mayweathers reflexes he may not have gotten hit.
Hopkins has 5 losses and 2 draws on his record, that means he has been outsmarted 5 times, and 2 other opponents he could not beat. Mayweather beat all 41 fighters he shared a ring with, with 42 wins in 42 fights, he has never been outsmarted.
Surely you can see it's merits? Floyd has fought the better opposition than Bernard (with the exception of prime RJJ), and has never been beaten. He's outsmarted every opponent he faced as a professional. Hopkins has not, he's been beaten 5 times and drawn twice. Just because he resorts to headbutts, low-blows and faking low-blows (against Calzaghe) to buy time when he's exhausted and getting beat, doesn't mean he has a higher ring IQ than Mayweather.
Hopkins has basic boxing abilities...I never seen him walk down a southpaw, with his foot on the inside...That would be stupid in his opinion,..Thats a fun challenge in Floyd's mind
Floyd is the smartest fighter in the game imo. Even Hopkins said Floyd's ring IQ is just as high as his. He even said Floyd could fight until he was Hopkins age. Floyd has always based his wins on being smarter than his opponents.