You could replace your title with "Barcelona players or Real Madrid players?"
Most of each team fans are gonna argue they have the best players or at least most of them are the best because that's the team they cheer for, while some other few impartial fans are gonna give you a proper analysis of each team lineup and players. The difference in overall quality is nearly nonexistant, altho there is probably a different mindset and ways of training, playing, communicating, and so on.
But in the end the question doesn't make any sense. Both teams are great and have equally strong lineups, whether they are the champions or not is up to chance. Someone has to be the winner, doesn't necessarily mean the loser sucks or is much worse.