Barca is far stronger than Milan. They have secured winning La Liga and CL is the only thing they are fighting for. If they do the impossible and come back from the first leg result, they will win the whole thing.
So what? It's not about teams, if there will be no Barcelona, Real, Bayern in the next CL you will say that now it's easier to win it for Juventus, isn't it?? But you should look deeper - don't look at the names, look at the system