Well, there is also price and features. I've got a Kobo Elipsa, it was an impulse buy at a book store and I regret it because for just a little bit more you can get a Remarkable 2. The Remarkable is lighter, less bulky, faster, and has this fantastic warm backlight. The Elipsa felt like outdated, heavy tech from the start, isn't waterproof, and its notetaking functions are unusable (it's just too slow). The OS is rarely if ever updated.

Equivalent Kindles seem to be much cheaper cheaper, though, and with overall better features and maintenance. And the store is much larger. The downside is obviously that you make yourself dependent on a fairly evil company that destroys culture and the lives of many aspiring authors. But most people don't care about that.