Which Monuments?

The way I see it you have 2 pairs - 2 cathedrals and 2 Moorish Palaces.

Cathedrals - if you only want one, it's a matter of opinion in which. These are two of the most important and beautiful churches in Spain, so there isn't a consensus of which is "better". I simply prefer the style of Seville's, but this is totally subjective. Look at pictures and see which speaks to you. Another factor is balancing your time - is there more other stuff you want to see in Toledo or Sevilla?

Alhambra - I hear the night visit is quite different than the day. That said, if you are seeing the palace at night I suppose you don't NEED to see it in day either. But you might want a garden visit in the day - you can get a daytime ticket for the gardens and other sections without the palace. Does this count as a monument to you?

Sevilla's alcazar is very impressive and has wonderful gardens as well. I'd see it if possible.

These 4 are the must do sights in these 3 cities. There's lots of other amazing things, but these are top. The other musts are experiences - San Nicholas viewpoint of Alhambra, Flamenco Concert in Seville, and just walking the narrow lanes in all 3.

Ann -

There are a great number of cathedrals/churches in Spain that might be classified as "must see" by different folks. In addition to Sevilla and Toledo are Leon, Burgos, Santiago de Compostela, Salamanca, Valencia, Barcelona, among many others, depending on your personal views/perspectives. I could tell you what my personal favorites are (Burgos and Valencia, btw) but that is only my opinion. You may very well prefer one, or several, others.
Opinions are much more in agreement when it comes to Moorish palaces and grounds - the Alhambra in Granada is the runaway favorite.

The cathedrals you happen to have named are rather different from each other. So I don't see them as duplicative. In any case, you can't visit too many churches in ... Rome, for example. Seville is a very pleasant, walkable city. I'm not sure why you would go so far (I mean to Granada) just for a second visit. I happen to have been to Granada twice because of one business trip, but why wouldn't you go someplace new, like Ronda or Carmona or Santiago? (I know that the usual answer, here, to that question is, "Barcelona", but you didn't mention it.)

Day 1. Granada - Alhambra
Day 2. Travel to Sevilla
Day 3. Cathedral & Alcazar
Day 4. Travel to Toledo (via Córdoba)
Day 5. Toledo sights

All good food for thought. I am returning to both Seville and Granada since I'm going with a friend whose never been and these are on their bucket list.

We are also going to Salamanca so I guess theres another cathedral to consider.
For Seville I think we will do the Alcazar and the royal apartments and are also considering a Countessa mansion with great tile work.
I've seen flamenco but for my friend would you see it in Sevillle or Granada and where?
Thanks

There are actually two cathedrals in Salamanca - the "new" cathedral which is gothic and was built mostly in the 16th century and the "old" cathedral. a Romanesque building from the 12th century. You must go through the new cathedral to gain access to the old.

"are also considering a Countessa mansion with great tile work."

GO! This was one of the highlights of Seville for me. The full name is the Palace of the Countess of Lebrija.

Ann,
All the monuments on your list are amazing & different.

My question to you is this... How will you manage to visit Sevilla, Granada & Toledo if you only have 5 days?

You mentioned that you've visited the Alhambra Palace before, but your friend has not.

Are you sure you want to do the night visit (which is limited) compared to the day visit?

Have a wonderful trip!

Edit to add... We enjoyed a one hour Flamenco show at, 'Casa de Flamenco', while in Sevilla. It's a small venue, so you'll want to buy your tickets at least a day or 2 before. Keep in mind that there are no drinks or dinner served, only the show.
Enjoy!

We get in the first day to Seville at 3:40 the end of September. Planning on seeing Flamenco show and dinner. The Biennial Flamenco is there with a show in the Alcazar gardens and other locales but some local places like Koko and Nino de Alfafla look fun too.

Next day doing Alcazar with Royal Apartments and Cathedral. Trying to decide which to do first. The cathedral doesn't open until 11. We are morning people. Deciding whether to enter into Alcazar at 9:30 and then do Royal apartments at 10:30 or enjoy gardens and do a later time Apt slot before it gets too hot or do Cathedral first and then do last Royal apartment tour at 1:30.
Any advice?
We are doing 2 nights Seville, 1 night Granada, 2 nights Toledo and 2 nights Salamanca. Doing night Alhambra for different experience.

Flamenco - I went to 2 that were strictly music - no drinks, no meals. I preferred Casa del Flamenco - nicer setting in a patio. The other (don't remember the name) was a small theatre setting.

Alcazar with Royal Apartments and Cathedral - Depends. . . How much time do you think you'll want at the Cathedral (are you climbing the tower?) and how disappointed will you be if you are too late for the Royal Apts? Why not go to the cathedral after a leisurely visit to the Alcazar? Maybe they've changed the system but when I was there last year, you had to go up to the Apts entrance and sign up for the tour. We arrived too late for the last (1.30) tour - I didn't understand why, perhaps no one else had signed up and they'd cancelled. We got there about 1.28.

I've been to a couple of flamenco shows in Sevilla on separate trips, and enjoyed both, Auditorio Alvarez Quntero and last month, Casa de la Memoria. Both are about an hour, and strictly muscic/dance. Of the two, I liked Casa de la Memoria better, but only as the performers were a bit better, but at both locales they change nightly, so that may have just been the days we went. I hasve also heard favorable reviews for Flamenqueria, (Casa del Flamenco) but haven't been there myself.

I think we're going to do the Alcazar and Royal apts and decide after on the Cathedral. Have read mixed reviews on the Cathedral and not crazy about climbing the tower with tons of people. I would be disappointed not to see the Royal apts.

It's not a matter of 'either, or' if you have a full day. Plenty of time for both.

Someone posted yesterday that you can reserve/buy places online for the Royal Apts and then skip the ticket line to get into the Alcazar.

Climbing the cathedral tower is unlike others. It was built sothat the king could ride his horse up. Thus, it is a wide ramp, allowing people to pass each other easily in both directions. The main reason to climb is for the views. I'd expect it to be crowded at the top, but with people leaving all the time. The only other part of the cathedral interior that sticks in my mind is Columbus's tomb.