I do love my mini to read in bed and travel with, but lately I have had an issue were the point I am in a book isn't transferred to other platforms. I used to be able to move from my mini to my larger iPad, and to my mac. Now, it's sketchy at best. Although I can usually find the highlighted bit that I stopped on the other platform. Odd, huh...
I have been using my iPad air in bed, and it's okay. It's too big-ish, and too bright, which I find odd. It seems to me, my opinion, that it's brighter at minimum than the iPad air. *shrug*
But traveling with a full size iPad could be a chore. I usually bring a real book, and acquire a few magazines on trips, and the weight starts to accrete, and at the end of a trip, I often end up trudging through airports hauling more than I should be. What with chargers, power blocks, sun glasses, book(s), cables, headphones, ear buds, cases, meds, snacks, liquids, water/soda, salty snacks, etc, there's a lot. Using the mini helps a little with the drudgery of travel.
On the 'paper white' e-reader screens. I tried one for a short time. I didn't like the display. It seemed 'muddy', washed out, not very good to be looking at for long periods of time. Plus it's basically one use. Watching a movie on a 'peper white' e-reader screen would be rather insane. Unless they have changed, the update rate was annoying. Watching anything with any motion, would be just nasty. Yeah, no...
And why would I want to carry around a 'paper white' e-reader, and an iPad? If the choice comes down to that, it's iPad all the way. I remember the RocketBook (might be slightly off the name) which was one of the first e-readers in my knowledge. (Although I have a Sony 'DataBank' which might predate those) They died for a variety of reasons I'm sure. Making them limited like that means they are not going to be ubiquitous. Unless you can do many things on the same device, that device ends up limited and unusable compared to others. But they are cheaper, so... They do have a market, but some are high priced too, which is kinda nuts.
Anyway...