In Barcelona 3 nights. Want to spend 2 more in Spain. Train to Madrid? Want to eat tapas, drink wine and hear music with the natives. 60 year old couple
It is always a good idea to visit Madrid.
Both cities will offer what you are looking plus a lot more.
I’d stay in Barcelona. Two nights means one day and that isn’t enough time to get a good feel for Madrid. You can always take a day trip from Barcelona if you want to go someplace else.
You can also look into visiting Girona and Tarragona
Another vote for Girona, a one-hour train ride to the north. Picturesque and with easy transport to beaches or to Salvador Dali sites.
Very strong reputation for restaurant cuisine, too.