Last I checked, Kobo will be better specs (screen, water proofness and connectivity) for the money, and if you’re technical it can be modified very heavily, including pretty easily user expandable storage.

Kindle will have a more seamless Amazon experience and maybe better support.

I have a Kobo Clara HD, and I love it to bits. Warm temperature backlight, and I have installed custom firmware on it which lets me use a different reader app, and run an SSH server on it so I can remotely transfer files etc.