I'm visiting Barcelona for 3rd time. I want to visit one other city, traveling by train, some place spectacular, charming, historic and unique. Valencia is closer, but i think Granada may be the better choice? Your thoughts, suggestions?
What time of year?
First two weeks of March
I would choose Granada so that you can visit the amazing Alhambra. Spend 2 or 3 nights in Granada. Visit the Alhambra during the day and also reserve a magical nighttime visit. You must reserve Alhambra tickets well in advance.
You might want to look into the Fallas Festival in Valencia in March to see if it appeals. I've been twice, and it was great fun.
https://www.visitvalencia.com/en/events-valencia/festivities/the-fallas
Whichever is easiest to get to for the amount of time you have. Each is worth 2-3 nights. Time of year you intend to visit may be a determining factor.
Because I’ve been the Granada four times, I’d pick Valencia as I’ve only spent limited time there. If you think you’ll return to Spain, go to Valencia and plan an Andalucía trip in the future.