Working in the industry, I can tell you a bit about both fabrics / brands. But I'll stick to giving the low down on NeoShell.
Firstly, NeoShell is not related to eVENT. In-fact it is arguably the first proper blur between soft-shell and hard-shell (i.e. not a simple lamination of membrane to fleece liner).
Compared to eVent, which has air-permeability of around 0.1CFM* (depending on face fabric used), NeoShell can be incrementally "dialed" to have 1 or more CFM, with its hydrostatic head dropping as you head upwards.
The hydrostatic head may only be around a metre – hydrophobic PU doesn't have ePTFE's exceptional water repellent properties. But with its decent DWR it will be effective protection in most conditions, and the PU structure can stretch and recover, which ePTFE cant, making it truly 'soft'.
But back on the CFM issue, hot plates and sweating dummies can create all sorts of test results in labs, but what Polartec say is that a higher CFM unarguably offers higher breathability. 1CFM compared to 0.1CFM… it's obvious which "breathes" a big order of magnitude more.
Polartec may have taken polyester fleece from us Brits (I wouldn't say they fleeced it -groan-!!), but I've got a lot of love for Polartec.
Oliver
* CFM = Cubic Ft per Min – a measurement of wind resistance. A smaller value = less wind penetration.