Actually, it's silicone (not synthetic) brake fluid that does not attract water. The brake fluid that is labeled "synthetic" is still glycol-based; the "synthetic" label is more of a marketing tool than anything else. The manufacturers claim that because the glycols are not naturally occurring molecules, they are "synthetic".

As far as silicone brake fluid goes, you probably want to stay away from it, for several reasons, but the biggest one is that if your power brake vacuum booster is leaking, any silicone brake fluid that gets sucked into the engine will burn into silica (sand) which, as you can imagine, is not a good thing for internal engine parts. Glycol burns off harmlessly. Silicone will also cause a "spongy" brake pedal. Silicone's advantages are that it will not absorb water and won't eat your paint if you spill it. But for later model vehicles you are better sticking with a glycol based fluid.