I can't comment on the Kobo, since I've never used one, but I've had an older model Kindle for about 6 or 7 years.

I rarely use my Kindle any more. About a year ago I started using the Kindle app on my tablet and phone, and just kind of ghosted the Kindle. The app is easier to use, automatically syncs last read position with my online account, and when I begin reading a piece it is downloaded local, so I can continue reading when I have no continuity (such as on a plane when I'm in airplane mode). There is even a desktop version of the Kindle app for PC and Mac, if you want to read using a laptop.

The best part of all this is that you don't need to buy a Kindle to use the Kindle app, you just need a free Amazon account. Download the free app onto your phone or tablet, create an Amazon account (if you don't already have one), and download a few free pieces for test reads.

Hint: Configure the app to use white text on black background. It's easier on your eyes and uses less power than a brightly lit white screen.