I can't find any numbers for the Kindle Scribe so I guess no one has tested yet. But I also bet if Amazon was proud of the number they'd be shouting about it - especially if it was better than the others.
So Remarkable and Supernote are probably fine for another generation at least.
This is all pure speculation though.
I do have Supernote and the writing is as good as it gets for me paper-wise, my brain is fooled into thinking I am proofreading text printed on paper, which was all i wanted from that device.
As far as reading is concerned there is no comparison, the kindle wins on nearly every metric.
I just wish they would offer a kindle with a 10" display.
I will probably get the kindle scribe once it has been out for a bit, has good reviews and a software update.
When my Kindle (or RM) dies, I'll almost certainly replace it with the new writable Kindle, especially as I assume it's backlit which I feel is something really missing from the RM.