Hasselblads are smaller, lighter and more elegant than the RBs and RZs. I own a Hasselblad and have worked with a couple of photographers who used the Mamiyas, and have used one a few times in the past.
RBs are workhorses, versatile, rugged, big and heavy, and a little clunky. I won't argue lens quality between the two systems. The "look" is a little different, but quality is no argument.
So, if you buy a Mamiya system because it's comparable in quality to Hasselblad, and you buy it cheap at the bottom of the market, what are you going to lose? You'll be able to sell it for close to what you paid for it. If you pay more for the Hasselblad system, you'll still be able to sell it for close to what you paid for it. Yes, used prices might decline a bit, but you'll still be able to get a good dollar for it. If it's in good shape and well cared for, buyers will appreciate that. It's a Hasselblad, after all.
I bought my 503cx 3-lens kit with metered finder, one back and some other accessories, in EX condition,
for $3500 about 6 years ago. I added a used back along the way. I probably could get $3,000+ for it today. Yes, the price is less than what I paid, but I've had 6 years' light-to-moderate use out of it. If I was going to sell, which I'm not, I figure $500 to use the camera for 6 years is a pretty reasonable rental fee. (I keep an eye on KEH's used prices as my price guide, and I keep my kit in good repair.)
Peter Gomena