I've bought a Bronica SQ-Ai myself this week so i'm slightly biased in that direction.
I researched the Hasselblad (and every other MF SLR i could find) and while it's certainly the better camera you pay for it, and if you want anything other than the standard 80mm lens you'll be paying through the nose for it. The big advantage i could see was the large range of accessories and bits for the Hasselblad as the company is still around and the old stuff is very popular keeping it in circulation. If you have the money to spend the Hasselblad is the better system i won't deny that.
The things that swayed me in the Bronica direction were obviously cost, i bought a prism head, body, 80mm PS lens and a 120 film back for about £400 a good £200-300 less than a 500C/M, i could buy the 40mm lens with that extra money whereas a Zeiss one for the 'blad is about £600-700 alone. Some Bronica bits are expensive, like the AE Metered prism head, and film backs are a little pricy in the £50-90 range, but that's more of an issue if you want multiple backs.
Weight, one often overlooked but important, the SQ-Ai is probably the lightest MF SLR as the body is mainly polycarbonate rather than metal, this doesn't bother me though but might bother others who prefer mostly metal. Having held the camera i can't imagine lugging around anything heavier.
I couldn't find anything terrible said about the Bronica SQ-Ai during research other than people saying it's no hasselblad but that referred mainly to aesthetics and lack of metal rather than image quality from the lenses which is considered on par with the Zeiss stuff. The only problem is with finding a readily available supply of accessories for the system. Lenses, bodies and film backs aren't uncommon though harder to find than more popular systems (Pentax, Hasselblad, Mamiya). Some of the more unusual films backs like the the 6x4.5cm one and the two 35mm ones (24x36 and 24x56 pano), new focus screens, speed grip, metered prisms are harder to get if you need them right now.
I can't really tell you what to buy it's just my perspective and you should do some of your own research to see if it fits your needs.