I think another the reason for the co-production of RB/RZ systems was because many people were skeptical of the electronics and potential for battery failure (whether it be on a long, demanding shoot or outside in battery-defeating temperatures). Yes, there are work-arounds that we're all familiar with now, but that's like Monday afternoon quarter-backing (after the Sunday game) - hindsight almost always gives perfect clarity.
Originally Posted by EdSawyer
For my purposes, I (generally speaking) have chosen not to buy cameras which require a battery and chose the RB67 Pro-S for that reason. In hindsight, I wish I had chosen the Pro-SD, but I'm very pleased with my Pro-S all the same (even the 120 backs which need to have the light-seals maintained). My 35mm gear all requires a battery for some level of functionality (whether just for the meter or for both meter and shutter), but I tend to prefer the least amount of electronics for my film gear.