I got my RB67 after selling off my A900 in 2013, and took it out to a anime convention.
My issue was originally the plain focusing screen was a bit weird to use and got a lot of vibration. I had to add some foam bits to the WLF and resealed the adapter. Got a split prism focusing screen and got myself sharp ever since.
Got four lenses, the 90mm Sekor, the 90mm KL(The best normal lens), the 180mm and the 65mm Sekor C lenses. For easier use, I got the handle with the remote shutter to further reduce vibrations and steadiness while out and about.
I guess I am odd for taking it out to Dallas for a walk around with my kit and a NPC Polaroid Back for obvious reasons.
It's a fantastic system, further enhanced with my C3 and Universal Press for all sizes.
There's two upsides for the RZ system, better lenses (you can find the K/L lenses for the RB, but more expensive) and prism metering capabilities that are far beyond what was available for the RB.
RB67 if you need a mechanical tank that will be useful almost anywhere, in any climate and no electronic parts to burn out. Or the RZ for "faster" shooting and newer parts availability.