I'm not sure Barca would fare as well in the PL, or Madrid. Just my opinion, but La Liga is very attacking based, whereas PL is a mixture of attack and defence, perhaps more defence. The physicality of the League would not suit certain players of Barcelona or Madrid.
A few years a go, that might have been true. Foreign imports took a lot of time to settle in the PL. But now it's different, because they are coming in and tearing it up.
Mata, Silva, Michu, Carzola have all come into the Premier League and have settled easily. Mata and Silva have cases to be the best players in the league. So i don't see why Messi & Co would have problems.