taste sherry or see Cordoba....

I'm not a big fan of sherry so perhaps not a fair question. That said, Cordoba is great, and well worth at least a brief stop. The sherry would have to be awfully good (or you would have to be a serious sherry fan) to justify skipping Cordoba for that, IMHO, but only you can say what you care about.

Personal preference, but you can taste sherry in Sevilla, so I assume you’d like to take a bodega tour. They are similar to any winery, so of your two choices, Córdoba and its Mezquita wins hands down. It would be difficult to combine Córdoba and Jerez in a single day trip since they are in different directions.

ez, Cordoba with a stop at a tapas bar for some sherry.

Which white hill towns? I think you could easily add a sherry bodega tour in Jerez if you are planning to visit Arcos. There are a lot of interesting sights in Cordoba besides the must-see Mezquita. I would never encourage anyone to skip Cordoba. If you are really interested in the production of sherry, then an hour or so touring one of the bodegas might be a good thing for you to do, otherwise just drink a few glasses while you're in Sevilla. How many days do you ahve in Sevilla? You could take the train to Jerez and tour 2 or 3 bodegas. Add the horse show at the Royal Equestrian School and you've got a good half day trip. Or make it a full day by adding Cadiz as well.

I agree with everyone else - Cordoba!!! The Mezquita is magnificent, but Cordoba also has many other interesting sites. And it's a very pretty city, with its white-washed walls, narrow alleys, courtyards and flower pots. We spent 2 nights there, and it was one of the highlights of our trip.