I have a Libra 2 and a Libra Colour. I generally don't notice a difference in crispness, though the effective resolution of the colour's screen is lower. There is a huge difference in the contrast, and you will probably want to use the frontlight even in a reasonably bright environment.

It is maddeningly impossible to get an ereader with all three of these features: b&w screen for maximum crispness; physical buttons for reliable page turns; modern processor for speed.

I'm happy with my Kobo Clara Colour. As far as the specs go, both are 300 PPI when displaying black and white. I took a picture of my screen from as close as my phone would allow - the lens was basically touching the e-reader [1]. My eyes can't really focus at this distance anyway, so I can't complain. I don't use the colour screen much, but seeing the book covers in colour is fun for me.

[1] https://imgur.com/a/cszqi0F

Yes, I replaced a B&W Sage with the Libra Colour, and used them for a bit side-by-side. Contrast (not sharpness) of B&W text is slightly worse with the color one, but not by so much that you'd notice it if you weren't comparing them next to each other. The resolution of actual color is worse, but obviously you can't get color at all on the B&W one, so hard to argue that this is a downgrade.

Unless you're a real contrast freak, I think most people would be slightly happier with the color than the B&W; but it's definitely not worth paying extra for.

Yes. I had color Kobo, forgot it in the airport lounge, and bought BW one as a replacement. It is much better.

I use a bw Boox device, a colleague has the colour version of the same device. The colour version does not show text more blurry, rather, the contrast is significantly lower. I personally prefer the bw device.

I compared. On the color version, the text seems to have a slightly fine mesh or rippled texture. There's no huge difference, but I prefer the black-and-white version