I've been experimenting with this lately and here is what I've found. The mesh jackets are okay until it gets real hot, like 95+ then they don't seem to do very much to keep cool. Took a Kilamanjaro and opened all the vents so the jacket could catch all the air and let it run out through the back vent......too darn hot. Put on the perfed leather leaving the sleeves loose and guess what? I feel cooler at the higher temps due to a little sweat being able to catch the air in the leather jacket. It really surprised me to find myself actually cooler when moving with the leather vs the mesh, but I guess the mesh doesn't allow the sweat to build up enough to get the cooling effect. Just a thought, but it has convinced me, plus I get the better protection.