Would you spend a day in Antwerp or Leuven?
There is a bit more of interest in Antwerp than Leuven - Leuven is only small, whereas Antwerp is a city that can rival Brussels.
Lavandula
Antwerp is a city that can rival Brussels.
I think that Antwerp is the city many hope that Brussels will be.
But for a day, both have charm, maybe Leuven would be smaller but good for the time you have.
Thank you!