Non D is pretty bad overall, nothing like the 55mm non D.
As already mentioned the optical composition is the same between the 45mm and 45mm D. You get the clutch and a metal barrel, but guts are pretty much the same.
I own the 45 and know it's limitations, and tried a D, after reading early reviews, but found it to be pretty much the same. Others report vast improvements, so best case is see if you can try one from a US dealer, DT out of NY or CI,, in Atlanta.
My usage was on a P45+ which is 1:1 crop. Its even worse on the 54 x 40 sensors. If you are going to use the 1:3 crops, (IQ140, Credo 40, IQ150) this more than likely will be a great lens.
If you want a sharp wide, i.e. 28mm to 40mm in a Mamiya mount that will give you full coverage sharpness, you might need to consider a tech camera and Schneider or Rodnestock glass. Sure the new 40-80mm seems excellent but at a very high price.
Paul