Does anyone still wear a hat?
Choosing a hat is important. You'll be wearing it for 4-8 hours most days. Your hat will become an extension of you, a part of you. You'll feel naked without your hat.
I actually traveled with two hats. I had a wide brim, vented hiking/safari hat and then a baseball cap for the late afternoons. Why two? Well, I loved my hiking hat, but after using it on long hikes at home, I discovered it got rather wet with sweat on long hikes. It needed to dry out. And, the sun remains high in the sky well into the evening in Spain in the summer--so I knew I'd want a hat for the late afternoons as I wandered the villages and towns after my daily "chores." It's up to you and your preference.
I liked the safari style with side snaps (that allow you to turn up a side of the brim and attach it to the hat). This proved really useful on windy days. I'm not a physics or math person, but there's something that happens when you roll and snap a side that keeps the wind from taking your hat away.