Valencia vs Malaga

I would plug the train travel into the Renfe website and see what maximizes your time. I would lean toward three destinations over four on a trip of this length.
When will you see Madrid of both days are spent on a day trip? Have you been before?
Malaga is definitely too much travel, but people often pair Cordoba and Granada with Sevilla.

Do your dates fall from March 15-19?
https://www.visitvalencia.com/en/events-valencia/festivities/the-fallas

Traveling from Seville to Valencia is a lengthy endeavor. Malaga is far more doable, but Cordoba and Granada are great. Or, you could do a tour of the "white villages."

@valadelphia our longest train ride will be from either Barcelona to Seville or Valencia to Seville, around 6 hours, but we do not travel high speed train often so it will a unique experience on its own. Next train ride would from either Seville or Malaga/Granada to Madrid for our last three nights.

A vote here for Cordoba!

If you’re losing significant time to reach Sevilla - 6 hours, I would recommend staying there at least an extra day to increase to four days. I am a fast traveler, but I am spending another four nights in Sevilla soon, and this will be my third time there. Cordoba is on the route - either coming or leaving Sevilla to end at Madrid. My preference would be to go to Cordoba before Sevilla since I think Sevilla is the grander choice between those two.

I’ve been to Malaga twice and will be there again in February for their Carnaval. I wouldn’t go that extra distance to add Malaga.

I haven’t been to Valencia, so I am unable to provide advice for that option.

Eleven nights is really short for Barcelona + Madrid + Andalucia. Three nights may be difficult in Barcelona as the first stop. So much there requires prepurchase of timed entry tickets, and you may not be operating on all cylinders if you're arriving on an overnight flight. As already mentioned, you have allotted 3 nights to Madrid, which is just 2 full days and some extra hours, yet you are planning two side trips from Madrid--to cities that are not in the same direction and each of which has a lot to see. So I'm worried you may end up somewhat frustrated in both Barcelona and Madrid, feeling as if you don't have enough time in either city.

I liked all the places mentioned in this thread, but for me Malaga and Valencia don't have quite the "wow" factor of the others. (In truth, I'd say the same about Madrid if the visitor isn't into art museums.) Getting to Valencia would take considerably more time than slotting in Cordoba, so that's two reasons I'd skip Valencia on this trip.

Seville is a place where I agree four nights are warranted for most visitors, if not more. And then there's Cordoba. Those two cities could easily occupy the 5 nights you have available after accounting for Barcelona and Madrid.

If using trains you could save about half an hour (each way) in travel time by visiting Malaga instead of Granada; the calculation for bus travel is probably somewhat different. But I think we'd be hard-pressed to find even one person who would recommend Malaga over Granada. The Alhambra is stunning. It really needs at least a one-night stay (I don't see that you have time for the usually recommended 2 or 3 nights).

@acraven Thanks for your response and everyone else's. Thinking of your suggestion of an extra day in Barcelona, skipping out on Valencia and Malaga then adding an extra day to Seville/Andalucía. We are not big on spending hours in museums so itinerary will likely be 4 nights Barcelona, 4 nights Seville and 3 nights Madrid.

While everyone is different, I think that will give you a good balance. I hope you'll have enough time for Madrid itself to decide whether you want to return for a longer visit. There's lots more to see in Spain, and Madrid is a very convenient gateway.