[Quoth]

I've had or have a Kindle DXG, PW3, Kobo H2O original and Kobo Libra.
I have other eInk also as well as two kinds of 10" tablets.

1) The DXG is about 9.7" @ 150 dpi, I think (I thought 167dpi, but a search gives 150dpi). If it was true grey scale rather than "white", black and roughly 14 in between grey scales it could do PDFs better. Actually a 6" PW3 (300dpi) does PDFs better, though it's too small.

2) It's slow

3) Next generation eInk screens after that are a lot whiter.

4) It's too heavy to sit reading a novel for hours.

5) Obsolete. No-one knows how long Amazon will allow downloads for it.

6) No touch.

7) No front light, though I don't often use a front light.

8) Terrible for collections and annotations compared to any Kobo from Touch onwards. No collections without registering.

9) A S/H model might be blacklisted or have wrong FW to connect to Amazon or register.

10) Not much storage, which can't be expanded externally.

11) I bought it for PDFs, it's useless for most of the PDFs I have. I now use a 10" Android LCD tablet for letter/magazine/A4 size scanned PDFs and the Kobo Libra for smaller PDFs. I use GIMP ->mng file -> imagemagick to crop PDF margins, resize, brightness, contrast & bit depth.

A 7" Kobo Libra is about €100 cheaper than a 8" Kobo Forma here. It's the fastest eReader I've used yet. Similar "white" to a paperWhite 3 and both are better white than the PW4 I borrowed. Both are slightly less white / bright with no light than the Kobo H2O original which with light off, which is about 6.8" @ 266dpi, it's long gone.

The Libra is far better than DXG, manages larger page size PDFs, has page turn buttons.
I use my Kindle simply to buy occasionally from Amazon, using "Download to PC & USB transfer option". Then backup and convert to epub2 with Calibre. You may need a plug in from Apprentice Alf to do this.

I check Smashwords & Gutenberg before Amazon, download ePub from Smashwords, but mobi from Gutenberg and convert with rules to epub to fix their style concept.