The main differences are that you would have access to Amazon v easily with Kindle, and can email docs to your device.
Although kindles typically get discounted more frequently. It depends on what you’d like in the devices. Personally, I couldn’t get it to work on my MacBook though I’m not v tech savvy. You can look over here for Apprentice Alf and Kindle DRM removal if you do a search and familiarise yourself with Calibre (a library management system that has plugins that can allow for such a process). You would have to remove the DRM to get the books bought on one system to another device from another ecosystem.