I expressed my opinion in comparing Kindle and Kobo in this post:
https://www.mobileread.com/forums/sh...le#post3926698
The only thing I forgot is that PW3 is a little faster than KA1. KA1 is not really slow but I can see the small difference between them. But the comparison should be made between devices now on sale.
And about the eventual bias in favor of Kindle: may be, many reviewer did not really use the device for some days before writing, they simply says: it is not compatible with Amazon's store so it is a negative point an so on. But serious people that do accurately their job will report strength and weakness of both.