The correct answer is "get both." Good disc brakes and tubeless tires are, to me, mandatory upgrades, and I'll never buy a new bike that doesn't have them. Upgrading to both doesn't have to be an expensive endeavor, but if you're on a budget, get the brakes first. Hybrid cable/hydro brakes feel a little different than full hydros, but the performance is pretty much identical. The Juin Tech units are available under other brand names, btw.