I've heard people say that eVent is more breathable, but the link I posted disagrees. I haven't noticed a difference myself, but then again I sweat like a horse and with any waterproof fabric breathability is relatively speaking. I just open all my vents or when splitting, but my shell in my pack for the uphill when weather permits.
"People say that marijuana smoking is going to get in the way of my career. I say to them that on the contrary, my fighting career is getting in the way of my marijuana smoking." -Nick Diaz