My CO J3 gave me a headache, but then it got damaged when an RAF Chinook helicopter flew low over my horse and me, and it hit the road! (with my head in it).
The RAF paid for a replacement - can't remember what its name is but it's one of those that showjumpers often wear, with that silver stripe up the front (ventilated). It's the most comfortable hat I've had.
I also had a Troxel which was nice and cool but not a very good fit.
I don't have a recommendation but I do have a small tip, make sure that when you get the hat that you check that if the strap kind of goes round the back of your neck in a sporty neck covering type of way (really bad description but I hope you understand) that it doesn't sit on your neck, mine rubs terribley!
I ended up with a Dublin onyx which is the cheapest of the kite marked hats but was the best fit.
I wanted a Troxel Sierra but it was totally the wrong shape for my head.
I have the JTE junior switch! Its soo comfy. Its got a dial on the back allowing you the alter the tightness of the hat. I got mine off Ebay brand new and was about £40