What is the best professional car ceramic coating?

Most of the brands used by professional detailers are in the same league, and from the consumer's point of view, there isn't really enough difference to make a difference. Each will have strengths and weaknesses, but be roughly comparable.

There are a few brands which are sub-par, which is why you should concern yourself with who is applying your ceramic coating, rather than which brand they use. A skilled professional who is trying to maintain a good reputation won't use inferior products.