Here's my condensed version of what stones I recommend for pizza (from best to worst with a heavily slanted NY style/high heat/short baking time perspective):
Nothing can touch this for thermal ruggedness and conductivity. Can be fairly expensive depending on where you live though.
Rugged and relatively conductive, reasonably priced, but you need a thick slab (1" is ideal), which can get a little tricky to track down.
Conductivity depends on composition, but, generally, firebrick is extremely rugged, dirt cheap but not all that conductive. Less conductivity translates into better heat retention, but, expect much longer preheats. Lower conductivity also completely rules out weaker than normal ovens. If you're oven can't hit 550 f. cross firebrick off the list (and track down soapstone).
Both thermally weaker and less conductive than cordierite at about the same price (or more depending on your local cordierite resources).
Unglazed Quarry Tiles
Conductivity can change depending on composition, but generally these have the worse conductivity of all baking stone materials. They also require extensive detective work to make sure they are food grade, as some unglazed tiles contain toxins.