I'm at the beginning of a three-month trip, and I just spent two days in Córdoba and five days in Sevilla.
Two days was the perfect amount of time to spend in Córdoba, though I think you could cover a lot in just one full day. Since it was the beginning of my travels and I have trouble adjusting my sleep patterns, two days gave me time for siesta.
I didn't take any guided tours in Córdoba. I used the RS Spain guidebook, which had an excellent self-guided tour of the Mezquita-Catedral. He gives it 3 triangles, which is barely enough. He ought to have a 4-triangle option for the most extraordinary sights, and this would definitely qualify.
I also visited the Casa de Sefarad (1 triangle is fair), the Synagogue (no triangles, probably fair as well), Casa Andalusí (no triangles, and probably not worth the visit), Plaza de las Tendillas (1 triangle is fair), and the Living Museum of al-Andalus (1 triangle, maybe should be 2). And just walking around the city was a 3-triangle experience. I went to the equestrian show at the Royal Stables, and I didn't really care for it. Supposedly the horses are well-treated, but to my admittedly uneducated eye, they seemed like they were in distress.
I ate at three restaurants recommended in RS Spain: Taberna La Viuda, La Posada del Caballo Andaluz, and Mesón San Basilio. All three were fabulous.
I had a reservation at Hotel Posada de Vallina, recommended in RS Spain. Since I arrived very early (9am), my room wasn't ready, but they offered an apartment in the San Basilio area, about ten minutes walk, that was ready immediately, and that was perfect. I loved staying in that neighborhood, and I was still able to go back to the hotel for breakfast each morning.
Five days in Sevilla were more than enough. I had a lot of downtime, but I didn't mind. With that much time, though, it might be worthwhile to consider a day trip.
I did a tour of the Cathedral and the Alcázar with Naturanda, recommended by a few folks on this forum. My experience was not positive. First off, they were very disorganized getting the tour started. And the size of the group was way too big, around 25 or 30. Our guide, Emilio, was excellent, but the whole thing felt very rushed, with little time to linger and pay attention to the details. I would definitely recommend visiting these two sites using the self-guided tours in the RS guidebook, so you can go at your own pace.
I did the RS audio walking tour, and even though I'm not a fan of the banter between Rick and Lyssa, it was a very good orientation.
On my first evening I did a Tapas, History, and Local Customs tour with Spain Food Sherpas. There wasn't a lot of history, but the tour was so much fun! We hit four different tapas bars. We were a group of 11 (12 is the max size), and our guide, Carolina, made us all feel like a big family. (Some of us went out for drinks afterwards.)
I also did the City Walk with Sevilla Walking Tours (Concepción Delgado, recommended in RS Spain) on my last day in Sevilla. I tried to get tours with her to the Cathedral and Alzázar, but she didn't make the 4-person minimum, which is why I went with Naturanda. Her walking tour was excellent, and even though I'd already seen a lot of Sevilla by then, I learned a lot, and she put a lot into context.
I stayed at an excellent Airbnb in a great location.
I had a great meal at La Azotea. Thanks to those on this forum who recommended it.
I went to a flamenco show at Pura Esencia, across the river. It was great!
Rick gives 2 triangles to Hospital de la Caridad. I'd give it 1. He also gives 2 triangles to a walk of Triana (the neighborhood across the river). This is also overrated, in my opinion. And he gives no triangles to Plaza de España, which I think deserves at least 1.
If you want more detail, send me a PM and I'll be happy to share photos and more.