A have a GPA show jumping hat and I LOVE it! My head doesn't sweat in it at all. It's the second one I've had, (I had a bad fall in the first one so had to replace it.)
I've got a Champion Ventair skull and love it. Used to get headaches everytime I rode and a new hat was the last attempt before I quit riding. That was 3 years ago and I've not had a headache since I bought it.
I used to have the peaked version too, but broke it when I landed on my head out XC, got the skull now and both are brilliant, couldn't recommend them any more highly!