The Mamiya Zooms, longer focals and D primes are metal bodies too -- only the original 45, 55 and 80 AF's had composite bodies. And I'll stack my lenses -- especially the newer D lenses -- next to anything from Hassy on optical quality too... For whatever reason you want to choose, the equivalent Hassy H focal lengths are generally both larger and heavier than the comparable Mamiya focal.
I wasn't dogging any other system. I was just stating some facts about Hasselblad lenses so there is no need to get all defensive about your Mamiyas.
As far as weight differences there isn't much between the Hassy and Mamiya D ones... If you can physically feel the difference of a couple ounces or a pound then WOW! That is quite the skill you have yourself there.
For example:
Mamiya 28mm D = 1.9 lbs // Hasselblad 28mm 1.87 lbs.
Mamiya 120mm D lens which is manual focus (says their website) = 1.8lbs // Hasselblad AF 120mm lens 3.1lbs
Mamiya 75-150mm D = 2.5lbs // Hasselblad 150mm = 2.13lbs
Hasselblad's 35-90mm aspherical lens is only 3.1lbs as well.
The heaviest lens in the arsenal is their 300mm which is 4.7lbs
The H3DII-31 weighs in at around 5 lbs as a complete camera (with battery, cf card and 80mm lens) where the Mamiya body only, no battery is stated on their site as being 3.lbs right there.
If the difference of a pound or two is the deal breaker for someone l then I think they should get a gym membership before getting their next piece of gear.
Optical quality is one thing if you want to start at charts all day. All in all, it's the final result that counts.
For example, have fun correcting your lens distortion, APO, moire and vignetting on your own while I have Phocus take care of it all for me with the click of a check box.
So how good is that optical quality now?

They also have totally different designs with the central leaf shutter compared to Mamiya's focal plane shutter (i.e. their 645AFD III).
That difference of 1/125" on the Mamiya sync speed compared to Hassy's 1/800" sync speed can be a deal breaker for many...
Long story short, we are not comparing apples to apples. A Holga weighs ounces but I wouldn't compare it to a digital camera in quality, specs, features or lens optics... As you can see my friend, there is a lot more to camera's then just its weight.
As I mentioned before, I was just stating the facts about the Hasselblad lenses and their weight is NOT JUST because of central shutters.