Well, I think if you offered Pep, right now, your choice of M, S, or N for your choice of any of his forwards, Pep would take the deal without even thinking about it. I would say. at least for right now, Pique is the best defensive player in the world (OK, maybe Hart). Yes, I would take Pique over either Luis or Silva.
Sure, there is real class on the RM roster, both in the first 11 and plenty of depth, the only league they would not win would be La Liga (probably come in 3rd). But no sane person would put their group "infinitely better" than Barca. I would not say BM has a better squad than Barca. Just to start with, no combination of any number of BM players is as valuable as Messi. There is such a tendency on this forum to undervalue Barca players, it seems like almost a requirement for being able to post here. "Must be willing to say terrible, untrue things about at least some Barca players." I count 18 truly world-class players on the current Barca roster. You don't even want more than that on your team, there is not enough playing time. Maybe a couple of those 18 you would not want to have to play major minutes, but on this squad they don't have to.