Really depends on use. With white coat pockets, the Mini is much more useful than the full size iPad. I can just drop it in my pocket and not worry about leaving it some place.
I actually found the Mini to be LESS eye straining than my iPad 3. I found staring at small font on a Retina causes more eye strain. It's almost like my eyes are working harder trying to find the tiny pixels on a Retina screen and getting strained from doing that. Whereas I have no problems reading from the Mini or from my non-Retina 11" laptop.
To each his own.
I actually found the Mini to be LESS eye straining than my iPad 3. I found staring at small font on a Retina causes more eye strain. It's almost like my eyes are working harder trying to find the tiny pixels on a Retina screen and getting strained from doing that. Whereas I have no problems reading from the Mini or from my non-Retina 11" laptop.
To each his own.