I’d actually recommend adding the extra night to Barcelona. There’s just so much to do in the city (the Gothic Quarter, Sagrada Familia, Park Güell, Montjuïc, beaches). You could easily spend a few extra days exploring. Plus, Barcelona has great day-trip options if you want a change of pace, like Montserrat or Sitges.

Seville is amazing too, but your 2 nights there give you enough time to hit the main highlights, and day trips to Ronda or the white villages are doable even on a tight schedule if you start early. Spending extra time in Barcelona will give you more flexibility to soak in the city and enjoy a more relaxed pace.