First, let's solve the 120 vs 220; Realistically, 220 is no longer available. There are some still out there, but pretty much all the manufacturers have stopped production.
If you like the feel of the Hassys, look into Mamiyas Systems. A whole lot less money, and you can get Leaf Credo (digital) backs for them that are far more affordable then Hassys, which may or may not matter.
I prefer the Mamiyas as I like the 6x7 vs the 6x6, love the rotating backs, and the systems are much more affordable.
Developing your own B&W film is incredibly cheap and easy. See this post on what you'd need.
The advantages to removable backs are that you can pre-load them for quick re-loading, and you can load different types in each of the backs, so you will have a choice of what to shoot. I keep 3 backs loaded all the time - 1 Color 100 (or 160), 1 B&W of assorted breeds and speeds, and 1 color 400ASA.
Anyway, the Bronica is a good camera, but it's older then the RB/RB's, and with the Bronica you're limited to 4.5x6. With the RB/RZ, you can do 6x4.5, 6x7, and 6x6 (I think there is even a 35mm back/kit available). I had a Bronica (SQ), and while the build was good, the RB is worlds better. If you like the 4.5x6, look at the Mamiya 645 series.
I'm a bit of a Mamiya fanboy, but in reality, I don't think there is a 'bad' MF system camera out there.