Both fine arguments. What is a high bitrate worth if the transfer was futzed with? Even at a lower bitrate does the consensus seems to go Criterion, and is that just because of reputation?
I can't argue about the quality of screen grabs (as was mentioned before we don't really know if they are trustworthy- I think of them as more of a signpost than a definitive evaluation).
Unfortunately, unlike film some reviewers back in the day, there is no one reviewer yet who I know and trust.
Therefore: I have the Criterion and ordered the Optimum. I will make my comparisons. And then I will go back to CAPS, and DVDbeaver and see how much I think they got right or wrong.
At least then, I will have established a rudimentary baseline for their judgment calls.