I think it comes down to your point of focus. With peach and peach 2, The eyes change shape quite a bit. Humans notice that much more than other aspects.
In general, I think the "ours" method could benefit by moving the boundaries between colours in and out until they get an average brightness match with the similar area in the nearest neighbour version. A lot of the "ours" images have a higher proportion of black.
In general, I think the "ours" method could benefit by moving the boundaries between colours in and out until they get an average brightness match with the similar area in the nearest neighbour version. A lot of the "ours" images have a higher proportion of black.