I have trained no-gi Jiu Jitsu for a couple years and have been at different gyms.
I have trained at Mat Chess for a few months now, taking the no-gi grappling classes and love it.
Mat Chess differentiates itself in two ways.
1/ Technique - First, Andrew (head grappling coach, JJ black belt under Dave Ginsberg, owner) is awesome. He has a fairly structured way of delivering techniques class after class. In essence, he is progressively distilling his "system" (not a term he uses per se - he uses the term strategy), which as far as I can tell is not the plain vanilla Jiu Jitsu you might have learned initially but rather a straightforward, yet unusual and effective view on it.
I personally love that it's all in control, even in scrambling situations. It's solid technique that is delivered with great attention to details that matter. Keep your eyes peeled and listen up. This is high quality content you will not find on youtube.
2/ People - This leads me straight into my second point, which is about people training at Mat Chess. Folks overall have a very control-centered game as opposed to a scrambling game - i.e. in my opinion Andrew trains folks to become "technical". This means often times, you can't get in or out of a situation just by scrambling or muscling your way through. You'll have to know what you are doing. Likewise, many students will quickly capitalize on common mistakes.
Bottom line: I personally go there to improve my technique.
In a couple months, I have seen my grappling progressively improving and becoming more solid, going from aggressive nonstop scrambling to tighter control and cleaner transitions.
I still have a long ways to go but Andrew traces a nice roadmap for his students to follow to meet the highest standards of Jiu Jitsu technique.