Kobo vs Kindle

I really need an ereader mainly due to strain on my eyes from my phone but my biggest dilemma at the moment is that I at least need an ereader that doesn't lag or glitch or isn't too slow for the page turning.

The lag that they showed on/with the Colorsoft frustrates me or any sort of slow scrolling/page turning like I've seen on some ereaders. It would honestly take me out and makes me never want to get any ereader.

Another issue for me is that a lot of ereaders are only back and white but yet the only thing I want in color is my book covers. Them not being in color irks me, I honestly never even thought that this could be an issue but I would prefer a fast none lagging/glitching ereader.

At the moment I'm stuck between the kobolibra colour and the Paper white. Part of the reason I'm stuck between the 2 is due to KU's wide selection of books and i think I'd be fine getting used to the black and white covers rather than the lagging or glitching on other devices.

I'm also open to other devices as long as they're not slow.