Again, please feel free to correct me if I'm wrong as I've never owned one but I don't believe even the White Industries freewheels are as well sealed as a cassette hub. I have a friend that does a lot of single speed off road riding and he said the ratchet on his was contaminated with moisture and grit after just one wet muddy ride. He uses cassette hubs on all his off road bikes now. It was on his advice I went for a Pompetamine with a Hope SS cassette hub.
Again, please feel free to correct me if I'm wrong as I've never owned one but I don't believe even the White Industries freewheels are as well sealed as a cassette hub. I have a friend that does a lot of single speed off road riding and he said the ratchet on his was contaminated with moisture and grit after just one wet muddy ride. He uses cassette hubs on all his off road bikes now. It was on his advice I went for a Pompetamine with a Hope SS cassette hub.