They're good cameras. I have an older S2A system.
However, if you're thinking of going pro and you live near a large city where equipment rental is a possibility, you might do better with a Hasselblad or RB or RZ-67 system, so you can rent the exotic high-end lens or four extra backs or extra body when you need them. Hassy and RB/RZ will also offer a clearer path to digital. I don't know that any of the digital medium format backs are made with adapters for Bronica.