M92 has wifi, you could do basic web browsing. There is evopedia ported for M92 - you can use Wiki offline (I hope it is still true in new firmware).
There is SD card reader in M92. You may have lots of books. And transport of data is easier.
M92 has TTS (text to speach), you may install aditional dictionaries, play few games (chess, gomoku, sudoku, ...). Beside annotating you may also draw/sketch.
What was very annoing for me on K DXG was that it was not possible to organize files in tree structure. Kindle showed everything in alphabetic or date of use order. It is complete disaster if you have 1000+ of papers.
e-ink have both the same, but I am not sure about processor and RAM memory. M92 is few years younger, so I guess it might have more memory and more processor power.
M92 is smaller than K DXG because it lacks keyboard. So, it is easier to carry.
Android if successfuly ported should be available for "old" M92. Nothing is sure until it happens reality.
If you are Amazon oriented and can wait few months. I would wait for android port. You would gain advantage of both worlds.