Hi X, while neoprene may add something like assistance on the inhale and keep their shape more open, even with min loop volume, all of this probably falls under the "perceived" WOB category. I know of no hard testing that supports neoprene lungs having lower WOB on the same loop as cordura, do you? Also, it's harder to clean neoprene lungs and I have been told that they are easier to rip and generally less tough.
As for other WOB variables, axial scrubbers with their typically longer grain boundaries, will always add to WOB as compared to a radial, with it's shorter grain boundaries. This helps explain why the AP CCRs test higher for WOB than other OTS units. It's probably also a function of their flapper valves being thicker than say the Prism. AFAIK, the Prism has the lowest WOB of any CCR tested by the USN-1.6 J/L. As for the CIS, I believe there is test data somewhere that shows the hydrophobic scrubber membrane brings the WOB up significantly. Supposedly Boris is slightly lower than the Prism, but it has big diameter hoses and as with all BMCLs, the WOB probably differs quite as lot as one moves through different body positions, which is one of several reasons why I'll likely never dive a BMCL unit ever again... -Andy