Here's what I've observed while researching ereaders for my first purchase.
B&W (e-ink) screens are easiest to read under most lighting conditions. It is easier to add light in the dark (for e-ink... not a backlit screen) than to take away light (for LCD displays like a laptop) if reading outdoors in sunshine.
The color LCD screens just cannot compete with e-ink in bright light. Inside, the color screens are killer. The e-ink screens have excellent readability in all lighting conditions except darkness. But it's simple to turn on a light or add a book light in that case.
Wait a few years and you will likely see color e-ink displays.
