New York has a very specific relationship with matcha. The city treated it as an aesthetic object before it treated it as a tea tradition, and the result is an interesting split: there are places that understand what they're serving, and there are places that understand how it photographs. Often these are not the same places.
Cha Cha Matcha
Cha Cha Matcha is fun. I want to say that before anything else. The Soho location is well-designed, the branding is sharp, and the staff are fast and pleasant. The drinks are also sweet, cold, and heavily accessorized. They are matcha in the same way a vanilla latte is coffee: technically present, aesthetically dominant, somewhat beside the point.
Matchabar
Matchabar in Williamsburg takes itself more seriously and earns most of it. The menu has a wider range of preparation styles, the straight matcha is actually straight, and they can speak to their sourcing with specificity. It's not a tea house in the Kyoto sense. But it's the closest thing Brooklyn has.
But what about Kettl?
The actual answer to the question "where is the best matcha in New York" is Kettl in Dumbo, which I visited the next morning and which operates closer to the Ippodo model than anything else I found in the city. Japanese sourcing, minimal menu, prepared correctly.
NYC understands matcha. It just understood the aesthetics first and is working backwards toward the substance. Every city goes through it.