I have a Bronica GS-1 and have used an RB briefly.

I use the Bronica about half the time for static subjects on a tripod and about half the time handheld. I tried using the RB handheld, but found it very difficult. It wasn't so much the weight, but that the focusing is with a rack and pinion. This means that you pretty much have to hold almost all of the weight of the camera with one hand while focusing. With the Bronica, the helical focusing allows you to support much of the weight of the camera with the palm of your left hand while still turning the lens. I also find prisms to be a great advantage when handholding (and even on a tripod when the camera needs to be higher) and the prism for the RB is a monster.

For tripod only use, the RB has some advantages, closer focusing with bellows, rotating back, maybe waist level finder if the shot requires the camera to be lower than eye level (though the Bronica has a rotating angle finder that accomplishes much of the same thing). For handheld use, there is no question, the Bronica is much easier to use.

The AE finder for the Bronica shows the shutter speed chosen in aperture priority mode or the shutter speed you choose in manual mode. The GS-1 is a electronic camera and requires a battery. The RB is all mechanical. I can't remember if there is a metered finder for it (the RZ is electronic and you can get an AE finder). The RB requires cocking the shutter and winding the back seperately, something I found awkard, but not too different from the view cameras I used for years (the RZ fixes this).

If you get the Bronica, I would recommend you get the 110 macro lens for your standard lens instead of the 100mm. I have both (got the 100 first) and kept running into the minimum focusing distance. The 110 macro is a great lens and has enough close focusing that I don't have this problem anymore. The Bronica lenses have smoother bokeh if you are in to that.

John