Which EPD should I design for?

An EPD from http://www.eink.com/ is ouf of question, as they don't sell to individuals.

But there are at least two others, that sell EPDs to individuals, have informative documentation and even offer development kits:

• http://www.pervasivedisplays.com/
• http://www.good-display.com

So which one should I go with?

My prerequisites are to get a small EPD around 4" with a good resolution.

I first looked at this here: http://www.pervasivedisplays.com/products/441, but it has only 113dpi (400x300 px) which may be suitable as an electronic shelf label, but not ideal for an e-book reader. This EPD is only black/white (1 bit color).

Then I found this here: http://www.good-display.com/products_detail/&productId=167.html which has awesome 230dpi (800x600 px). There is even a development kit based on an STM32F103xx with schematics and complete firmware code which should be easy to migrate to a STM32F303xx. This EPD is black/darkGray/lightGray/white (2 bit color).

I guess I will get one of their kits to experiment with before designing my own hardware.