I sold my Mamiya 7 for a Hasselblad, only rarely regret it. The Mamiya is of course more portable, and far nicer to use handheld. For tripod use, I think the SLR beats range finder, and the Hasselblad wins there.
If you're not planning on using a tripod much, Mamiya every time, if this camera will live on a tripod, Hasselblad every time.
I like the 'blad, interchangeable backs etc. but if asked for a recommendation, I tend to say Mamiya simply because you can carry it about like it's a 35mm camera.