[Quoth]

I can't see how capacitive, no matter how well done, isn't slightly dimmer than IR as an extra layer with semi-transparent conductive material is needed. IR doesn't add layers. I don't want to have to use the lighting to compensate. Certainly the Original Kobo Aura H2O is a brighter white than my Kindle PW3 or my friend's PW4 or any ereader I've seen.
I think capacitive is a backward step on eink simply done as a cost reduction and a way to have a less recessed screen. It's actually a very old technology and the only reason smartphones used resistive before the iPhone was to allow high resolution stylus annotation, handwriting and poky GUIs derived from desktop (PDA WinCE). There isn't much difference in resolution between IR and capacitive, they are both very low resolution, though fine for fingers. The Wacom type tablet is rather different and it can be behind a screen, but only works with a special stylus energized by the tablet, hence it can have buttons and pressure.

Capacitive, properly done, even in 1980s didn't affect sharpness. Any difference between PW3 and PW4 can't really be to do with real advances in capacitive technology. It's really really old and can even use glass with zero effect on sharpness even 30 years ago.