I don't see much difference between the B1G and the Z1 system. But whatever one you choose, I would get the quick release that tightens with a thumb screw, as opposed to the quick lock lever. The thumb screw allows for a wider variety of plate sizes, and can be tightened very tightly.

I have the B1G and the B2, and I've used both with 8x10 and 7x17. If you happen to find a used B1g, Precision Camera Repair can easily (and cheaply) bring it up to new specs.