Mike, I'm probably stating the obvious here, but when you bake a pizza, all the heat necessary to bake the bottom of the pie is stored in the stone. A thicker stone gives you more thermal mass, which, in turn, gives you a greater amount of stored heat.
When you put a pizza on a stone, the heat/energy travels from the stone to the pizza. A bigger stone, with a greater thermal mass will transfer proportionately less of it's energy reserve than a smaller stone. This also means that the temperature of the stone drops at a slower rate. Generally speaker, the bigger the stone, the quicker the bake time. This is why you can walk into a pizzeria with a deck oven heated to 450 with 1.5-2" slabs and walk out with a pie baked in 5 minutes. A 1/2" stone preheated to 450 would take forever to bake a pizza because it's thermal mass would store a fraction of the heat than a typical deck oven stone.
Gauging potential recovery time with thicker stones is a difficult task. A thicker stone
1. stores more heat and ends up at a higher temp after a pizza is baked, so it doesn't have to recover as much, but
2. the additional thermal mass will cause the recovery to take proportionately longer than the smaller stone.
1 and 2 most likely cancel each other out, and, from a recovery standpoint, the stones might act in a similar fashion, but there's way too many variables (the composition/temp/thickness of the dough, the wattage/btu output of the oven, the specific heat of the stone, the differences in mass, etc.) to know for sure.
Even in pizzerias with deck ovens with loads of thermal mass, you do hear stories of bake temps dropping/bake times extending during especially busy times when the oven has to handle lots of pizzas and the burner/element can't feed the stones fast enough. In other words, additional mass doesn't guarantee quick recovery times.
The one aspect where you will pay with a thicker stone is the pre-heat. As discussed before, the composite material will go a long way in mitigating any additional pre-heat times between the old 1/2" and new 1" stones, but... if you went with 5/8" compositie, the decrease in pre-heat time could be dramatic.
My recommendation of a 1" stone isn't related to recovery but to bake time. Depending on the actual composition of the CSF stone, there's a really good chance you'll be able to bake a 4 minute or less pie in an unmodified 550 degree oven. A 5/8" stone is going to extend that clock. Being able to bake a 4 minute pizza without oven tricks, is, to me, pretty convenient. If you're comfortable with oven mods and/or are pretty well settled in on longer bake times for the foreseeable future, then maybe the 1" stone is overkill. Also, if you're striving for the shortest pre-heat possible, then the 5/8" stone would be the better choice. If, on the other hand, you want the flexibility of shorter bake times without oven tricks and are relatively comfortable with your current pre-heat time, go with the thicker stone.
