For me its how well it blocks the sun
Both in terms of keeping the sun off, but also in terms of stopping sun getting in your eyes
Most baseball caps seem to have a light colour under the brim, which really annoys me - the light reflects back into your eyes
I want - no need - a hat with a black underside
Found this on special at the outlets on the weekend
waterproof (goretex 0h yeah! just what I need for sunny Ireland), windproof, light AND black underside
super
ok it won't protect my neck or ears but seeing as I tend to wear a UV Angler Buff anyway that doesn't matter