CS is also a for profit enterprise. As such the last I saw of them they were pushing some 'premium' account nonsense saying that premium account holders had an easier time finding places to stay or something along those lines. I have a real issue with trying to monetize something that started from a place of just wanting to help out fellow travelers out of the goodness of your heart so I appreciate that WS has maintained that they will continue to operate on donations alone, even though that means the tech might lag a bit behind.
I think raybo hit the nail on the head though. The main difference, as far as we are concerned, is that WS is aimed at cycle tourists, and the hosts are people who understand the specific needs of cycle tourists.