I haven't used either but the permeability tests I've seen show Neoshell being more air permeable. There's more to it than membrane permeability but its something to think about.
I went the other direction with Sitka/Proshell but I'm looking for a shell that can handle non-stop rain and brush, day after day. Neoshell and eVent might work too, but the Sitka had good reviews for this type of use.
