Milan is slightly bigger since it has more Champions League wins than Liverpool, thus being more traditional and having more continental presence. You can say that Liverpool had more recent success, but recent success does not make a club big (Looking at you, Blue Manchester).
The fact that Serie A is not as big as the Premiership (this now, because the Serie A was huge in the 90's) should not be something to consider, it's not Milan's choice to be on that league or not.
Milan is slightly bigger since it has more Champions League wins than Liverpool, thus being more traditional and having more continental presence. You can say that Liverpool had more recent success, but recent success does not make a club big (Looking at you, Blue Manchester).
The fact that Serie A is not as big as the Premiership (this now, because the Serie A was huge in the 90's) should not be something to consider, it's not Milan's choice to be on that league or not.