I have an insulated steel kamado (the keg) and a ceramic (Cyprus). Have been cooking on them for a few years. The problem of getting a ceramic temp down if you overshoot is a real thing. But keep in mind what RWalters said. It's only a problem if you overshoot long enough to get the ceramic heat soaked. Once you learn to control the kamado, pretty much not an issue any more.
That said, I have the keg as well. Kind of similar to the summit. I also have a hardware store about a quarter mile from my house that sells and demos both. The summit charcoal and eggs. Both are MINT.
My experience is that temp controll on ceramics is a little bit more stable than on a steel one. Not a lot. But a bit tighter. The steel will get hotter quicker. The ceramic will last forever, and even if I'm wrong about that the warranty is lifetime. Most steel models, as with the summit have 10 yr warranty. Steel is quite portable. Ceramics are heavy and if you try to lug it out on a camping trip or to tailgate at the football game you could Humpty Dumpty it or tweak your back. Pros and cons to both.
I might also add that I have never cooked on a Joe, but have inspected their older models. The new ones have upgraded hinges, spring assisted lift, and upgrades to the firebox design. And as RWalters said the DnC system and joetisserie I would take a close look at the Joe. That oval design seems pretty awesome as well.
