I've spent a lot of time (over 4 months) traveling around Spain since 2016. My experiences in Portugal go back to the 1980s, so this is not an even comparison, but I'd say that Portugal feels more laid-back than Spain. I'd have no hesitancy in choosing either country from that perspective if I were interested in relocating.
One possibly-significant difference is the extremely late meal hours in Spain, with dinner typically occurring after 10 PM and lunch after 2 PM. The late dinner hour is a problem for me (sleep issues, and I'm not supposed to have caffeine), but it appears to work for the locals.
Of the specific cities mentioned, I believe you'll find housing costs higher (possibly a lot higher) in Barcelona. On the other hand, that city has a great deal to offer in terms of sights and experiences. There's nowhere in northern Portugal (which area doesn't include Lisbon) that remotely approaches Barcelona in that respect. Barcelona is a place I could enjoy visiting for a long time.
Barcelona has a climate quite different from what you'll experience near the northern and northwesters coasts of Spain, where many of your other options are located. The Basque Country and points west tend to be overcast and coolish. Barcelona has moderate winters but can be fairly hot (and sometimes humid) during the summer. Santiago de Compostela is sort of notorious for lack of sunshine, by Spanish standards at least. I'm not sure how different Porto is from Galicia, weather-wise. The Wikipedia entries for cities usually have weather-summary charts. For greater detail (day-by-day, historical statistics), you can go to timeanddate.com.
Oviedo is an attractive, historic city, but it is most definitely not lively. I have read that the locals head up to Gijon for excitement. Oviedo wouldn't be my first choice of a place to spend a lot of time, and I'm 68 years old. (Then again, I was there during the summer, and I didn't notice any university students about; the academic year would have more going on.) Leon to the south is a lot farther away than Gijon, but it has a lively restaurant/bar district in the historic center.
I haven't seen much of the Spanish Pyrenees (which I assume are beautiful), but I found these parts of northern Spain especially scenic: Picos de Europa (very rural), the Basque Country and Galicia.
The local language in Galicia (Gallego) sounds a good bit like Portuguese, so learning the latter would give you a head start if you end up in Santiago de Compostela.