Southern Spain mid February 2025 for a month+ NOW 6 WEEKS

I have used Ronda as a base to tootle around the pueblos blancos in a rental car. I can't imagine finding enough there for 3 full days. On the other hand, Granada will keep you occupied and engaged at least that long.

Cordoba is my favorite Spanish city, and over several visits I've found lots to delight me, including small interesting museums, good walking tours booked through the TI and a much more relaxed atmosphere than Sevilla. So I'd recommend another night, or maybe even two, there.

Sevilla definitely has a lot to see and do. There are also 3 possible day trips: Cadiz (over 1.5 hours by train), Jerez (about 1 hr by train, horse show, sherry bodega tours are the highlights), and Arcos, a bit of a slog, train to Jerez, then bus to Arcos. An alternative is to spend 3 nights in Jerez and daytrip to Cadiz and Arcos.

Valencia has a huge festival - Las Fallas on March 15-19. The city is packed, and it's truly an experience you'll never forget. That's when I visited, so much of my time was consumed by the festivities and my sightseeing was limited to the highlights. If you can include those dates, I'd encourage you to do so. If not, I don't know how much time you'd want there. I think the city is best-known for it's architecture with fine examples of modernisme.

Malaga offers a lot to do in itself and from there it's easy to day trip to Nerja and Antequera or places on the costa del Sol.
https://slowtravelitalyspain.blogspot.com/2020/01/malaga-what-to-see-and-do-free-31-ideas.html
Granada is better for a longer stay than Ronda. (I agree with Chani that Ronda is good as a base to tour the area with a car. ) We stayed in Granada for 9 nights and didn't get bored. You need one whole day just for the Alhambra and I'd add the night visit too. Remember you need to book Alhambra tickets well in advance. This is our trip report:
https://slowtravelitalyspain.blogspot.com/2019/04/granada-in-march-trip-report.html
Nights and early mornings can be cold in Granada, much colder than the other destinations you are considering, although it can be warm and pleasant during the day.
You will need some form of heating in all the accommodation you choose if you are going in February, but especially in Granada.
Again I agree with Chani about Cordoba. It's much less touristy than Sevilla. I stayed four nights so three full days but I felt I hadn't had time to relax and enjoy the city. If you stay a few days, I'd recommend the free entry to the Mezquita at 8.30. You get to stay in for about 45 minutes but we loved to go every day, exploring a different section each time. I don't think I'd have enjoyed seeing it all in one go as much. Plus during the free time there are no groups of guided tours and so you can really feel the atmosphere and the magic.
Between Sevilla and Valencia is tricky. I stayed in Seville for just over a week some years ago before it became overwhelmed with tourists and it wasn't long enough. You can also day trip to Jerez, Cadiz and Carmona. I'm not so attracted by Valencia, but haven't been there so I can't give an opinion. Friends who have, loved it. From Valencia you could day trip by train to Cuenca. So probably just under two weeks in Seville and just over a week in Valencia?
I'd go to Cordoba after Seville and before Valencia for a quieter few days and to avoid doubling back.

Six weeks is an excellent amount of time to enjoy Spain. February is one of our favorite months in southern Spain. I was in Andalucía for 11 weeks Jan/Feb/Mar this year.

I suggest splitting the 21 nights evenly between Seville and Valencia. Both cities are worthy. We generally spend about 2 to 3 weeks in Valencia and maybe 4 to 8 weeks in Seville. Alternatively as you enjoy slow travel you may like to split your time more evenly between Cordoba, Seville and Valencia.

Cordoba is one my favorite cities as well, it’s full of hidden surprises and has a lot more to offer than just The Mezquita. We are heading back for a month on our next trip and always regret only staying ten nights. Each city is so different. I don’t notice much difference in the hordes between Seville and Cordoba. Valencia is generally more sedate.

4 nights in Granada is just enough. As mentioned The Alhambra is a whole day more or less.

The weather varies a lot between the cities. In Granada this Feb it was minus Celsius at night. Us crazy tourists queued at The Alhambra in a massive hail storm, regardless The Alhambra was still packed. Valencia is our favorite city climate wise. We always hit a lot rain in Seville. I have eight umbrellas from Seville, must remember to take one with me next time.

As a heads up. There is usually 1 or 2 direct trains daily between Cordoba or Seville to Valencia Joaquín Sorolla. Changing at Madrid is an option, but a nuisance factor. In some instances the MAD change can require arriving at Madrid Atocha, then changing stations to Madrid-Chamartín to Valencia. Something to be aware of when booking.

Thanks to everyone so far! What a great bunch of suggestions! I was quite excited about the Festival in Valencia until I realized how much the accommodations prices were during that time ;(

Looks like we will only stay in Valencia a few days at the end of our trip. Now splitting our time between Cordoba and Seville.

New itinerary: So far

1st week in Malaga (Booked)

2nd leg five nights in Granada (Booked)
Fly to Marrakech for six nights.(Booked)
Eleven nights in Cordoba (Booked)
Nine nights Seville

Fly to Valencia, stay four nights (Flight Booked)
We fly home from Valencia.(Flight Booked)
Does anyone know if the bus schedule from Granada to Malaga airport stays the same in February? The timetables online are not shown yet and makes it a little difficult to properly plan for our flight from Malaga to Marrakech

Could you fly from Malaga to Marrakech before heading to Granada? And then just fly from Marrakech to Sevilla and work your way east through Cordoba, Granada and then Valencia?

If you like festivals, we loved attending the exciting Cadiz Carnaval last February! We were there five nights for the first week of it. From Cadiz, we took the train to Sevilla. We did take one day-trip from Cadiz to go to the Jerez horse show performance, also.

Hello Jean, We played around with a lot of different Flight and other travel possibilities and this worked out much more practical and economical. Thanks for your ideas!

Thanks Nick, that is basically what I had assumed. Just wasn't sure if I was missing something because of the time of year.

The train takes you from Granada to Málaga quite effectively. Then, light rail is easy from the main station Maria Zambrano to the airport. Very convenient travel.