Marc, the very first thing a Neapolitan obsessive like yourself should do when changing over to an electric oven, is to take a long hard look at the broiler specs. Wattage, number of passes, coil thickness. If you're one of those lucky 1 in 200 people who has a broiler strong enough to do Neapolitan, then you should be buying a stone that can do Neapolitan as well, ideally without modding. If you fall into the group of 199, then the stone selection changes up a bit.
As you move into non Neapolitan bake times, steel has a considerable edge over SiC. It's quite a bit heavier, but it's less expensive and has a far more proven track record. You can find a metal distributor, and $40 or so later, you'll be baking beautiful 3-6 minute NY style pies- guaranteed. On the SiC side, you could, in theory, spend $100 on a shelf, and bring it home only to find out that the 5/8" thickness (on the 16" square shelf) doesn't have sufficient thermal mass for 3 and 4 minute bakes. Lightness is nice, but guarantees are better.
I'm not completely ruling out stacking the 5/8" SiC with something else (such as lighter weight steel), but that's uncharted territory as well.
I've contacted a few ceramic suppliers/kiln shelf manufacturers in hopes that I can find a happy medium of lightness, thermal mass and conductivity, and I'm relatively optimistic, but it's going to be a process- my guess is 6 months at least.
So, for now, for a lightly charred 3 minute bake, with enough leeway in temp to allow for some broiling during the bake, 1/2" steel is king.