Barcelona were very good today, but they were by no means unbeatable. Messi and Iniesta shone. The Milan team was just not experienced or mentally tough enough yet. To go into the second leg against this Barcelona team and get a result, you need an incredibly strong team. I think in the last 8 years only Inter Milan and Chelsea have managed to do it, with two unbelievably strong teams.
The defining moment of the match was Niang's chance before Messi's second brilliant goal. If Milan go into half time 1-1 with Barcelona needing to score 3 in one half, then it changes everything.
I personally would have gone with experience. You cannot win anything with kids. Having said that if Balotelli was playing today, I think Milan may have pulled off the result. I expect he will be the best traditional striker in the world in 2 years time.
As for the comparison between Serie A and the Premiership? Our top 6 is very strong, but the quality of the league really tails off after that. I am not even sure our top two our much better than Milan and Juventus. In Serie A the bottom teams are much stronger. Even when they lack quality they are all mini Norwich's. Mentally strong with discipline and perform well above their level.