For me, the main appeal of an e-reader (I still prefer physical books above all) is being able to read in bed at night if I'm up later than my wife. Plus e-books are cheaper.
My wife has one of the older Nooks, which is e-ink based, but also has a backlight. She likes it quite a bit. I used to have one, and I also really liked it. It's small (fits in a back pocket) without being annoying to read on, and is extremely light so that holding it up when I'm lying down doesn't wear on me.
I personally read mostly on my Galaxy Tab S2. I particularly like the Google Books app, because it has a "night light" (meaning it puts a reddish cast over the screen, which is important when reading before bed so I don't screw up my internal clock). The advantage to one of these is that I can get books from all over the place -- there are apps for B&N and Amazon, and Google also sells books. I got a bunch of ePubs from a Humble Book Bundle, and those I just upload to my Google Books library and there they are. Plus I can wander reddit or whatever if I want something a little easier on the brain.
Years ago, when I had an iPad 3, I did really enjoy reading on that. The higher resolution compared to my Android tablets made text easier to read, and iBooks was definitely the most aesthetically pleasing and polished-feeling of all the apps. But there too, you could get apps for Amazon, B&N, and Google. It's since given up the ghost. I don't really read on my iPad Pro, only because it's giant (I got the 12.9" version), so not exactly easy to hold for long periods. But on my lap or whatever would be fine, and there too lots of screen space + high resolution makes for a pretty good reading experience.