The existing 6" kindle white display is 212 ppi and 1024x768.
So a 1440x1080 display at the same 6" works out to be 300 ppi exactly (see
here), matching the resolution of the 6.8" Kobo Aura HD/H2O device. Now the only thing that may sway me to Kobo is sdcard support.
And whatever cost-saving/feature-killing Amazon decides to implement/maintain:
* low ram + slow cpu = crashes on complex pdf
* ridiculously low amount of storage: I would not be surprised if it's 2GB
* the speaker (and TTS) will probably never return
* capacitive only input so I can't turn pages with wet hands (when washing dishes)