Do you think he would be as ineffective if he was playing for Barca in South America?
He'd do better than he does for Argentina, but not as well as he does in La Liga.
Italian and South American defenders just have a much greater natural cyncism and nastiness than the Spainish, which would see Messi fouled more and harder.
Then you have the greater tactical ability in Italy and the decades they've spent working on stopping flair players.
Spain is just trying to learn that art now to cope with Messi and Ronaldo, having spent years just playing their own way almost regardless of the opposition and primarily trying to outscore the opposition.
Takes a hell of a long time to have the defensive knowledge that is fairly deeply ingrained in Italy, even if the ability of Italian defenders is fairly unremakable at the moment.
My point was that Real and Barca would win their games as comfortably as they are now (and with more or less the same number of goals) if they played in Serie A.
I don't think they'd win as comfortably, even if they'd win almost as often.
7-0 would be 5-0, 5-0 would be 3-0.
Not a particularly significant difference, since they'd still be comfortable wins, but a difference nonetheless.