cuben dude!
water proof is a hard thing to understand in the gear world. what's water proof when you buy it may not be water proof a few months of use. what are our options?
cuben stays water proof, it's like polyurethane weave with dynemma and carbon fiber (varies from manucaturer or order) then melted flat just enough, finally coated with some patented coating by northsail. this stays water proof for a long time

nylon + coatings
polyurethane- better than silicone but doesn't addd strength to the fabric and in some instances makes it weaker
silicone - awsome and not expensive and make nylon stronger but leaks after being exposed to abbrasion, dirt, oil.
pvc - stong durable, but heavey
do you think their gortex membrane is just a mix of sil and pu and pvc, either way it looks heavy