Comparison of two "b" letters from that image
(PW left, KT right).
Seems Amazon needs to do some font scaling optimizing for the new resolution, the PW has far too many "soft" (aka grayscale) borders.
/edit: Updated with the screenshots below. Upscaling issues are now by far not as pronounced (although IMO still there). THe major issue now is that at that font size (and style) the PWs font lines are 3 pixels wide (vs the KTs 2 pixels), so they appear more massive and generally less fine.