The human eye is the only real judge of quality. I inspect all of my books and mark them as to (my opinion) of quality.
Then I go back and fix them when I am really really bored
I have add duplicates turned off so I won't accidentally overwrite a fixed copy with an unfixed copy. If I think a different copy is better then I will manually delete the format and add the book. Mostly as long as they are readable I don't, but I have some Project Gutenberg that I may
replace with MR versions some day.
A bit of a pain, but bigger does not always mean better so I do it the best way I can.
Helen