If you are going to be running in the sand, stay away from buggies and try to go with a truck as light as you are willing to live with. Maybe an emaxx with beefed up drivetrain. If you don't already have them, go with rubber sealed bearings. They don't stop the sand, but will prolong your runtime before things start to give out. I get all of my bearings from Avid. They are $1 each and are a deal. As for keeping the sand out, it's almost impossible. Sand is amazing, it gets everywhere. You can seal the motor and I've had pretty good luck with that, but it's everything else that you have to worry about. Just about everything that is sealed with a rubber gasket will let at least a grain or two through. The longer you run, the better the chances of failure of some part due to sand. You can also expect accelerated wear of your suspension arms around the hinge pins.

Just go with something that will be cheap to fix. A factory team really isn't meant for bashing, it's meant for racing. At the risk of getting flamed, I'll go as far as to say that the FT version will break more easily than the standard version. If you are interested, I have an RC10T4 that I'm thinking about selling with a pair of maxamps 3S 4000mAh battery packs (brand spankin' new). BTW, I have all kinds of spare parts for it too.