I have a Kobo Libra 2 and I think the only extra features are that it's waterproof and you can do audiobooks on it via Bluetooth (you might be able to do that on Kindle too, I'm not sure).
I went with Kobo because I'm not a fan of Amazon and because I wanted to access a subscription service through it. With the optional sleep cover I never turn it off so it's always ready to go.