JMM is being totally underrated here.. I'll go out on a limb and say that JMM stands a good chance at beating PBF. I say JMM is the superior counterpuncher. PBF is a counterpuncher himself and usually does it while on the defense. Most of PBF's opponents are also exhausted in the later rounds because they spend so much energy on the offensive in the early rounds (to no avail against PBF's excellent defense). JMM style will force PBF to go on the offensive, not on his usual defensive stance. Also JMM has one of the best stamina in the sport today, he is one of the few who can hang in there against Pacman up to the last second of the fight. I am picking JMM by SD. By the way, PBF is not substantially bigger than JMM. If they stand side by side, size will not be an issue. I saw a pix where PBF stood besides Joan Guzman and their size is very comparable. Guzman (who fought at 122) is no bigger than JMM (who has never been below 126).
Mayweather is much better defensivly, better offensivly, more power, faster hands and feet, better reflex's and has a 5" reach advantage. Add this to the fact that Marquez is a counterpuncher and is not comfortable pressing and Mayweather would not press him meaning Marquez would be ****ed.
Ive noticed already how easily PBF fans flip out whenever anyone says something they dont like. Anyway, Mayweather is a great fighter. No doubt. But, if you saw his first fight against Jose Castillo, he really lost that fight. Unbiased, he lost. Well, the judges wanted to keep his perfect record alive that night. Because of this Castillo fight, and the fact Mayweather never won a gold medal, he is a great fighter, but not the perfect fighter his fans make him out to be. I think PBF himself knows he is not the perfect fighter. He can be beaten. So, I dont think it is out of the question JMM could challenge PBF.
Floyd's best weight was 130, where JMM is basically in his prime. A fight between the two prime for prime is totally plausible. Floyd easily wins though.