AC Milan is a bit outside the center in the area near a train station and the big cemetery. You'll be near a Metro station that is only a few stops from downtown. The Park Hyatt puts you right exactly in the center of Milan next to the Duomo and the Galleria. If you're ok with a bit of commuting and the slightly grittier neighborhood you should be fine and can spend the 200 Euro a night (or some fraction) on great food, shopping and taxis. I can see the case for either place depending on your budget and how much you value a stay in the posh center versus what seems like a good business hotel.