Most of Avedon's The American West was shot on 8x10, but yes he did use a Rolleiflex for much of his work.
Originally Posted by cjbecker
If you're thinking of something for headshots and you don't mind the bulk of the SL66, why not an RZ67? You could get it, the motor winder, two backs, and the 180 lens well within your budget. Plus you'd be able to shoot rectangles for vertical portraits without having to worry about cropping. If you must stick to a European camera, then go with the Hassy. If you're shooting portraits in the studio, that flash sync speed is a huge issue, and that's a weak spot for the Rollei. At 1/30th, you'll start to see fringing from the modeling lights on your studio strobes, and you can pick up motion blur from your sitters because the shutter is open so long relative to the flash duration.
Best bet though to eliminate or select one system is to try and rent the Hasselblad kit (try renting a Rollei SL66!) and see if you like what it does.