Here's my take. I have owned/own the following: 2x501CM, 500ELX, 50CT, 50CF, 60CB, 80CB, 150CT, 150CF, 160CB, 250CT. Still have the 501CM, 80CB and 160CB.
Now...for me in order of importance:
Expect to pay for a service some time in a year or two. If you buy old C lenses then some are lucky and will keep going, others start drifting (shutter speeds). The bodies can run forever but a serviced body will run smooth, a non-serviced body that is on its last legs will be rough to operate and may skip a frame or so. Also, a bargain back may be light-tight...for now. And may have spacing issues. Or not.
Focus screens: I just cannot use anything older than an Acute Matte. In fact my current screen is a plain Acute Matte D. Brightest screen I ever used. Easy to focus anywhere on the screen too. Very difficult to find though if you don't get one with the body. Then again, if you are the split-screen kind of person it doesn't matter much what you get.
Prism: I don't like using the WLF on my Hasselblad. I find it tricky to frame and focus. I also don't like the 45deg prism. I use mine 99% of the time with a PM90 prism (at eye level, like any 35mm SLR). Otherwise I get shots of people's nostrils. And I don't like those. Maybe you want to budget for one.
Lenses. You may like 85mm on your 5D but square is not the same. I just cannot work out wides on square, for example. Long lenses on the other hand are easier for me to frame. Loved the 250. 150 is a spectacular lens, either C or CF. The older C seems to render a bit nicer to tell you the truth. With all said, I still think the 80mm is the most versatile, though I wish it would focus a bit closer sometimes.
Also, the handling of C/CT lenses is very different to the CFs which is different to the latest CB/CFE/CFi. The latest will be lighter to focus and have nicer grips. The CFs are heavy abut at least have a rubber ring. The C/CT have cheese grater focus rings which if you get a heavy focusing (ie not serviced) lens can be painful to use. Also, the C/CT have a coupled shutter/aperture ring. Change one and the other follows to match exposure. So if you want to change exposure you have to lift a tab and move the rings. All the others work as you'd expect, free rings but you can push a button to lock them together.
Overall, a Hasselblad was my dream camera. I bought one (actually three), and was ecstatic when I first held it in my hands. It is a sublime machine to hold and marvel at the engineering quality. The image quality is outstanding. But now that I have owned a RB67 for nearly a year...I just have this thought in the back of my head that the swedish camera should go. Too much money sitting on a shelf and that Mamiya glass is just outstanding. Believe it or not, I find the RB easier to shoot with. The Haselblad gives my 4 shutter speeds to work with: 1/60, 1/125, 1/250 and 1/500 with the 80mm lens. With the 150/160mm lenses I get 1/125-1/500. The 160 is a f/4.8 lens for goodness sake (though it is outstanding, particularly in colour).
With the Mamiya I can go to 1/15. The square-ish format is easier to fit for prints. So there are a lot of things to consider. Not meaning one is better than the other, just different. So....here's the final advice: don't stretch the budget. Get just the 80 or just the 150. Learn the system, see if you like it, then make the next move. You never know, you may use it for two shoots and decide that it just isn't for you.
In the end, if you do like the Hasselblad, you'll end up spending lots more buying another screen, maybe a body, lenses, backs, etc...there is no escape!
