I wasn't aware 700 degrees on different stones were different....can you explain that a little more? What stone would be best?
Because of the differing conductivities and heat capacities, you can produce almost identical classic, slightly charred, NY style pizzas in the same amount of time (4-6 min.) with the following materials/temps
1/2" iron slab- 450
1 1/2" cordierite (commercial deck oven) 500
1 1/4" soapstone - 525
1" cordierite kiln shelves - 550
1 1/8" split firebrick - 600
1/2" cordierite (with feet/old stone/pampered chef, etc) - 625
1/2" dense quarry tiles* - 625
3/4" fibrament - 625
1/4" porous quarry tiles* - 700
*Quarry tiles can vary in composition (as can firebrick, but that varies less). Density/heft and lack of porosity are good indicators of a more conductive tile. Note: these are, for the most part very rough figures and most likely have a decent margin of error (+/- 25 deg.). The order of the list, though, from most conductive, to least conductive- that shouldn't change. Also, this is just from a hearth perspective. Dome temps and top browning is another discussion.
If you really want to expand your understanding of conductivity and heat capacity, here's one of the best lessons that I've found on the subject:http://forums.egullet.org/index.php?/topic/25717-understanding-stovetop-cookware/
That's conductivity with a focus on cookware. If you want to put traditional stone hearth materials in the mix, here's the specs for fibrament and cordierite:http://www.pizzamaking.com/forum/index.php/topic,5645.0.html
And here's the numbers for soapstone:http://www.tulikivi.com/www/kotien.nsf/WWWTakka/The%20characteristics%20of%20soapstone
As far as the 'best' stone is concerned, I'm a huge proponent of 1 1/4" soapstone slab. With the exception of iron/steel, which, to be honest, isn't all that viable as a pizza stone, there's nothing more conductive and there's nothing with a higher heat capacity. It's conductive enough to pre-heat quickly/evenly and transfer a substantial amount of heat to the crust, while not being so conductive that it loses heat when you open the oven door. It's also incredibly resistant to thermal shock and lasts through years of heat/cold cycles. Soapstone and cordierite kiln shelves are the only two stones that, without oven modification or broiler technique, give you a quick baking time/proper amount of puffiness in a typical 550 deg. home oven. Everything else extends the baking clock, which in turn, decreases quality.