The Cybook is probably the best 6" reader if you have poor vision, particularly when the new firmware arrives with folder support (you will want to use its largest library view so navigation will be faster with a folder hierarchy).
The OpenInkPot firmware on a Hanlin V3 is good enough for everyday use, but it is configured for good eyesight. See
File Navigation: Hanlin V3 vs OpenInkPot and
BeBook font sizes and types.