Hi Tim:
First off, if you compare the conversions side-by-side, you'll see the LR conversion actually generates additional image info by those few pixels; IOW there is an extra 10 pixels of hidden image revealed on each side of the image by LR/ACR. Thus there is no pixel squeezing or stretching going on.
The other thing to note aside from the huge difference in color rendition and exposure accuracy, is that LR/ACR tends to over-accentuate edge definition (relative to C1) in an attempt to increase the appearance of detail, but the real culprit is in the micro-detail where LR/ACR leaves it more smeared. Here is where LR/ACR really fails IMO; it generates an over-cooked outer edge with under-cooked subtle center, kind of like a poorly prepared pancake
. And as you pointed out, no combination of sliders will correct that or make it look as good as C1.
**However, since you seem particularly determined to make it so with LR, you might try decreasing the lum NR to zero, color NR to 10 or so and pump the detail slider way up to 50 or 60. Combine this with aggressive sharpening settings at low radius -- try amount 50 to 60, radius 0.5. You should end up a little closer to the C1 sharpness, but more visible noise and probably some color artifacts. If you do ultimately find a way to get there with LR, be sure to let us know your recipe -- and good luck!
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For portraits:
I really like my 150/2.8, but would certainly still own the f3.5 version if I couldn't or didn't want to afford the 2.8 version.
The 210/4 is nice too, and another great value, but a little long for studio.
Another lens I enjoy for portraits is the Hasselblad F/FE 110 f2 lens. It is all-manual on the Mamiya via the adapter, and thus more difficult to use, but generates some beautiful effects in people.
Mamiya made a manual focus 145 "Soft Focus" lens with adjustable front element, or an early D-O lens like Nikon's. It is all manual on the Mamiya AFD as well, but actually works very well and is relatively cheap (like $300) on the used market. I own one of these and really never use it, generally preferring my 150 or Hassy 110. I may be convinced to sell it if anybody is interested.
Finally there was also a converted Imagon portrait 120 (uses sink-strainer aperture disks) made in Mamiya 645 mount, though somewhat rarer than the 145 SF and more money. It has a relatively slow max aperture and user reports are mixed. I've never used that specific version on my Mamiya so cannot comment precisely, but have used them on LF cameras --- for whatever it's worth, I did not care for the effect very much as foreground bokeh was decidedly different than background bokeh and generated an "unbalanced" look to the files.