Coach seating on both Iberia and Vueling will be especially tight on these intra-European routes. If that matters to you, I note that MXP-BCN is a shorter flight than LIN-MAD.

But I'm not sure what class of service AA would book you into on Vueling, which is a low-cost carrier. If you plan on checking a bag, you might be safer with IB.

If the schedule change gives you the option to get a full refund, you could explore your current booking options to see if you can get the trip for less than you originally paid.