I have not tried the Vanson, but I have and use both the joe rocket mesh and the first gear mesh. Both are better than leather or anything else i've tried for hot weather.
Of the two I like the joe rocket better. The mesh is more open than the first gear, so even when standing still there is a bit more are flow. And the padding is denser on the joe rocket jacket, hence I suspect it provides better padding protection. Also the first gear jacket is a standard left hand side inside pocket with a button. The joe rocket pocket is just inside the the left hand top just past the zipper and it is zippered and nothing will fall out of it.
But coke does pour through it nicely when you have a coke bottle in your hand (0pened) and you reach in to pull out your wallet. Don't ask how I know that.
RB