I don't follow boxing too much, but here's my read:
Martinez dominated Chavez in 2012, but still broke his left hand and tore up his knee. After the fight Chavez tested positive for weed, not sure if that mattered...
Martinez he broke his hand again in his fight last April. He got knocked down twice by Martin Murray and should have lost that fight except it was in his home country so he got the decision. He's had knee surgery, shoulder surgery, and is 39yrs old.
Only thing Martinez has going for him is he's a true 160lb middleweight and 3" taller than Cotto. Is that a big deal? I don't think so...Cottos has been fighting at 154 for a while now, he was at 140 like 10 years ago, long time ago not like he just packed on the pounds for this fight.
Cotto is 6 years younger at 33, and he doesnt go down man. He's a tough SOB. He fought Pacquio hard at 145, Mayweather hard at 154, crushed Margarito at 154 (who was 4" taller than him). I think it's important he changed trainers to Roach after the second loss in a row (Trout), then beat that Dominican guy who also lost to Trout. Most of these fights went the distance.
I think at 2x the money, I have to put my chips on the younger Cotto here at "home" in the Garden.