The main attractions of the Hassy would be the lenses, ubiquity of used backs and accessories, and ability to rent lenses in major cities.
The main attractions of the Bronica SQ system would be price, handling (with the lever wind handle and a prism, it feels a lot like a 35mm SLR, and focus is quick), and if you want to go beyond the three lens kit you describe, additional lenses are much more affordable.
If I wanted just that three lens kit (presuming your budget is not unlimited), with the considerations you're making, I'd probably go with a Hassy. It's that fourth lens, though, that's going to be the pricy one if you want to expand. On the other hand, with the price of Bronica systems these days, you could get your three-lens Hassy, and get a Bronica with an exotic lens, if you decide you need an ultrawide or a long tele, and the lens and body will probably be less than the comparable Zeiss lens for Hassy.