I'll say it... Salinity is the "best", but only because it gives you a batch by batch breakdown of the actual elements going into your tank. That can be important for folks with large SPS
colonies / clams that do regular comprhensive dosing / testing.
I personally have used Oceanic and Seachem Reef with success (only bought the salinity because it was on special and 2 bucks cheaper than SR). I've also used Salinity and everything pretty much remained constant.
Like they said, the best salt is the salt that makes your animals happy and healthy, is available on a constant basis, and is at the price point you choose.