Stylisticly i would say Marquez should be Valeros kryptonite as by what we saw he might have been a cruder version of Pac and JMM just beat Pac convincingly. Something about Valero made him seem special to me though... not sure what it is. I think it was me watching sparring footage of him vs some good fighters that were much bigger then him... he was schooling them showing some good boxing skills (not just a crude banger) and to my shock he was pushing them back in a clinch easily. I suspect his power was something special, but we will never know for sure. And by lack of evidence i gotta pick JMM.
Valero was great at counter punching and had more power. The Demarco fight showed he was more than just a "brawler". This would have been a great match in which Im inclined to favor Valero and im a huge JMM fan.