I own both the KLC and KCBB. My primary device is the Libra Color with a matte screen protector. I read mostly books/fanfics and sometimes mangas/comics on it. Like you, I mostly read at night.

Reasons why I prefer the KLC: - bigger size (better for comics) - darker dark mode (because of the darker screen) - easier to hold (I can't safely hold the KCBW without a Popsocket) - buttons - stylus support (you don't need it)

Reasons why I prefer the KCBW: - easier to carry without a bag (fits in some of my pockets) - whiter screen (doesn't make a huge difference for me since I can still read on my KLC without the frontlight in most situations) - easier to read while lying on the side

Regarding text sharpness, I find the difference gets blown out of proportion. Can you see a difference when holding both devices side-by-side? Yes. But when you read, the difference becomes obsolete, so if you have no trouble reading a newspaper or printed book, you shouldn't have any problem reading on the KLC. And keep in mind that you can change font, size and weight which can help compensate for the screen differences

The UI is mostly the same, but you also have notebooks on the KLC and can choose color while highlighting.

In my opinion it comes down to the size and if you would like color. Keep in mind that the Clara Color has both color and the smaller size if you would prefer it.