Do you use a third party (like booking.com) or direct with the hotel? I'm looking at Hotel Murillo in Seville. Don't see any advantage to not going direct - unless I'm missing something.
Here's a pretty thorough discussion of booking.com (and other 3rd party sites) vs. booking directly with the hotel.
https://community.ricksteves.com/travel-forum/italy/booking-com-44c0db57-e6d4-4130-b072-25e527c81262
I like reading reviews on booking.com because they can ONLY be written by people who have actually stayed at the hotel. (And I have written a few myself.)
My husband & I owned a B&B for 9 years and would use websites like booking.com during certain times of the year to fill rooms. It was one way to be able to compete with the larger properties and at least get your name out there. While we did have people who just booked on the booking engines site we really appreciated the folks who would find us there but then go to our website & book directly with us - the 15% charged by the booking engine comes straight out of the property owners pocket and in that business 15% is a lot.
Support the smaller businesses - book direct - they really do appreciate it..
I also use sites like booking.com for reviews, but then book directly with the hotel. I like the hotels where I can book by email, so I can easily communicate with someone and ask specific questions before actually booking.
I like to travel with a loose itinerary rather than a strict schedule so I book most of my lodging only a few hours before arriving in a particular town.
I research places ahead of time using guide books, tripadvisor, or any other photos/reviews I can find. I'll put a handful of choices for each stop on a spreadsheet in my Ipod, then call ahead in the morning while I'm on the road. Spain is a perfect country for this style of travel. Lodging rarely sells out, even in places like Granada or Seville, and anything available in the morning is going to come at rock bottom prices. I regularly pay much less than the rate in guidebooks. In one month in Spain, I only had to go further than my first choice in Granada. Even then, with a couple more calls, I found a great room at a great price.
I do book ahead if I know I'll be somewhere at a given time. Plane and train reservations lock you in, so you might as well book your rooms - since you don't have any flexibility on those dates. I think you are always better off calling directly. It may seem easier to book online or by email to the hotel, but a phone call allows them to explain what they have and the price - then know you're booked before you get off the phone. A third party search engine often fails to allow for options you would consider acceptable, that you might be offered if you call directly (e.g. an apartment for only a three day stay, or two rooms vs. a family room). Email often has delays where you're unsure whether you're booked, or if they even received your email.
If the hotel's own web site has a booking engine that appears to show real-time availability and actually make reservations, then that's my first choice. If not, then booking.com may be an easier/faster tool to use. Email is one way to request quotes in advance from several hotels, which may possibly have some room availability that is not shown on aggregate sites like booking.com. Email is not best for last-minute booking because of the time lag, but a phone call does work.