The Fuji 645Zi is not really a rangefinder camera. You use the autofocus or a manual guess focus distance. It's advantage is a complete package without having to change lenses. The zoom is limited but very usefull. Also the cost isn't bad. One problem I've had is using a cable release. I normally use a tripod but still got sharper results with the release. Others may not have this problem. Anyhow with the release you can't lock in exposure or distance values, adjust the composition and expose. So if I want to use values other than the ones picked using the final composition I have to manually set them in. A true manual camera would be better.
I'd say if you can afford it go with the Mamiya 7. You will need to carry and change lenses. Bronica or Fuji Zi depends on how much manual control you want. I would think that the Fuji would be faster using the zoom and auto focus. I've had no problems using the Fuji meter but only for B&W and I sometimes lock exposure on a certain part of the picture. Lens is very good but my usual size is only 6x9ish prints. Also very good at close focus distance of around 3 meters.