Had 6' onyx. Replaced all textbooks in school with it. Then internal flash memory broke and I returned to reading on the phone.
I use speed reading module in KOReader and it'd need third crosshair, third glance per line on a wider screen. Considering how I plan to switch to zig-zag reading.. Mb I prefer phone size.
Most books I read nowadays are for studying, which means emacs, large screen.
I'll test a friend's reader and mb buy one if it really reduces eyestrain