Really tempted to go with Ramirez, simply by virtue that he could take shots from Arguello and Chapo without much issue and was a better pressure fighter than Castillo. However, it wouldn't be that simple and it'd be a damn good fight. Ramirez either late TKO or unanimous decision.
I'd be rooting for Chico, but I can't take him here. Ramirez gave a prime Arguello Hell, beat a prime Rosario, and gave a good account of himself against a prime Chavez. So, three guys who were a level above Chico.
I'll also take Ramirez but not with a ton of confidence. This a fight fan's dream. One of those matchups where you just know it won't disappoint.