Armoured
Well-known
Ignore what the store clerk said. Both can take great, great pictures. Try one out if you can. For that matter, don't overlook the Bronica and other brand variants on the Hassy style, if you're willing to try used.
By far the biggest differences you will notice are:
1) Rangerfinder vs. SLR. Not going to rehash this point, as it's a matter of preference and the task at hand.
2) Modularity: you can switch out almost anything on the hassy.
3) Waist-level finder: base finder for the hassy is at waist-level, which is very different. I like both, but I'm finding for medium format I mostly prefer waist-level. Waist level viewing both affects the way you frame, but also very much the way people around the camera interact and react. For some reason, waist-level gets more neutral reactions.
4) Handling: for all of the reasons above. I actually find the feel and size of the Hassy-style to fit nicely, whereas the Mamiya is more bulky. But that's me.
By far the biggest differences you will notice are:
1) Rangerfinder vs. SLR. Not going to rehash this point, as it's a matter of preference and the task at hand.
2) Modularity: you can switch out almost anything on the hassy.
3) Waist-level finder: base finder for the hassy is at waist-level, which is very different. I like both, but I'm finding for medium format I mostly prefer waist-level. Waist level viewing both affects the way you frame, but also very much the way people around the camera interact and react. For some reason, waist-level gets more neutral reactions.
4) Handling: for all of the reasons above. I actually find the feel and size of the Hassy-style to fit nicely, whereas the Mamiya is more bulky. But that's me.