Hard fight to pick, both good chinned and determined pressure fighters. I will always remember JLR as the fighters that popped Edwin Rosario's cherry in his backyard, after being knocked down twice, and against a hostile crowd.
If anyone is getting stopped its Jose Luis Castillo, I have no doubts about that. Ramirez stood up to absolute animals like Chavez, Arguello and Rosario. He has nothing to fear with going toe to toe with Castillo. Castillo is slightly more skilled and if he fights cautious he could edge Ramirez out, but if he goes in there and wants to play tit for that, it will be his ass. I bet it's the latter scenario, but if they fought a trilogy Castillo would probably adapt one time and sneak home with a decision.
If I had to pick a winner I would say Castillo could do it, taking a hard fought but pretty clear decision. When Castillo wanted to fight smart he had a pretty good defense, he judged the distance well and had a fairly strong, tight guard. But he could so often be dragged into a war, duking it out in the trenches, it almost seemed like he had this inexorable sense of duty to as a proud Mexican. Thats why there is every chance Ramirez could do what Soto and Corrales did.
Ramirez stood up to the bombs of Chavez, Arguello, and Rosario, all of whom hit harder than Castillo. He was stopped once in over 100 fights, and that was early in his career to Rubin Olivares. Ramirez was insanely tough.