I have had both types and would recommend either, make sure the valve stays shut or water will get in. I open my valve and shoot some caulk into it and close it for good. I ruined a pair walking through long grass and brush and then through ankle deep water, one boot took water and was never the same. The valve must have been opened(before i caulked them) and with the compression and decompression, sucked water into the felt soles. Just a personal expreience.
You might want to check ebay, a friend just got some new for 55+ shipping(buy now). The maufacturer is BATA on most, I remember hearing there is another one too.
ficious