You are getting $10.50 120 processing and scans on a Noritsu and are concerned about resolving power, then there's an issue and a whole other thread therein.
Pixel peeping scans cannot solve that problem nor the debate between film vs. digital. Your process is hybrid sounding like the crux of your dilemma.
The optical and focus capacities of the scanner create whole new level of interpolation. The only way to really compare is to wet print the Mam6 stuff and compare it to your scans. Then increase your scan quality via an Imacon or drum and re-compare. Then check it all out against digital for the shots you want. Now add up the costs.
Part of your self-created dilemma is economic: film is struggling to stay viable, affordable, and selective, so quoting a price is a value statement (will Portra even be around?). So is the time invested in any process only to have the rug pulled out. The durability of your Mam6 is also a big if (can anyone service them anymore?).
It sounds like you want a higher return on investment based on absolute sharpness vs. time of effort and value of equipment. That's an equation only you can answer.
There is a convenience factor to the whole dilemma.
Yes, If I was a resolution fanatic, I bet I could source out some obscure built-for-Government-spec-Kodak lens on some weird DIY rangefinder that would be about as practical as lugging a coffee table around to take a picture. And it would probably not open up wider than f8.
Convenience wise, the Mamiya is wayyyyy ahead of a Hassleblad/RZ67/folding 120/ LF field view thing, ( BTW- I have considered the Plaubel Makina) .
Ughhh, those things are bulky, if I pull a camera like that out in a crowd, small children start to cry, and people dart for cover. Not what I have in mind. The Mamiya 6 is perfect in that regard, I can carry that in a Timbuk2 messenger bag, pull it out while being relatively discreet, and not draw too much attention to myself.
The same cannot be said for a TLR. Admittedly I get self conscious, when I have to anchor myself, and peer down the chimney of a TLR. I look like a camera nerd. People stare at me and my steampunk contraption, so much for inconspicuous shooting. sigh.
I got jazzed by micro 43 at first, I was like, cool a small camera that looks like an amateur thing, but deceptively can take good pics with legacy Leica glass. Sadly the sensor is so small, and legacy lenses tend to not get as good a results as the lenses engineered with fault calibration correction built into the firmware (20mm Panasonic 1.7 is a great lens BTW).
So back to square one, I am seeking out a camera that doesn't announce itself, that doesn't scream "LOOK AT ME, LOOK AT ME!!!! AND MY HIGH END TOY",
that is small enough that people don't glance over with stitched eyebrows, curious as to what exactly I think I am doing. Yet knock my socks off when I review it in LightRoom. The Mamiya 6 is such a camera.