When it comes to practically I'll take my ebooks on my ereader. I remember the days when I was traveling and only had so much luggage space for the books I wanted to bring. I got a fairly large purse just so I could fit at least 2 or 3 medium sized books, but was never satisfied because I couldn't bring ALL the ones I wanted.
But now? Shoot, I have a little purse I can slip my Paperwhite into and out of with no problem. 2 books? 3? How about 50? A click of my fingers and all my precious stories are right there, taking up next to no space at all.
And the lack of weight is amazing to me! Those huge books could only be read from a few positions for ever so long at a time before my arms would tire and the handling became awkward. No problems with that anymore. They all weigh the same on my ereader.
I don't know about ereaders being hard on the eyes. I guess if you are reading from a phone or a computer or tablet that might be a problem, but ereaders shouldn't be difficult. I'm sure the Paperwhite could be if the screen grew too bright, but the lighting is readily adjustable, I can make it to where it's just as easy to read as a regular book. And there are other readers, like the Kindle Keyboard, that don't come with a backlight at all so it really does have the same "feel" as a page. At least to me...I do wish I hadn't broken mine.
Don't get me wrong though. If I had the money I would purchase all of my favorite "necessary" books in hardback. I never want my ereader battery to die unexpectedly and me being caught in an empty house without a single book to entertain me. Plus I can probably find better prices on used books than what their ebook price is listed.