I read on a few 6" ereaders of all the major brands. I also have a Kobo Mini whose 5" screen would be perfect for me if it had a front light. When I'm away from home I read on my 5.1" Galaxy S5 phone. That's actually perfect for me, or it would be if it was e-ink.
Some things are just really personal. I remember when I had an Audible forum we'd often discuss narrators and some that I thought were terrible were beloved by a lot of people. We're all different and ain't that nice.
Barry