I would go with the manix due to the fact that you want strengh, the sand should not be a problem due to the open construction, and if it becomes an issue just rinse it out.
I definantly recomend the hungarian folder, it is one of my favorite knives. As far as the cf and damascus caly, in my opinion it is the best looking spydy ever made.
Who else here is dissapointed that the jani-song is not available in the us? I am an avid flipper of the balisong, and i have been interested in the design for years. I understand the laws, but i would have expected them to make it in golden.