(old tech)Vizplex / Pearl E (new tech) I say you need to test out the device with each feature and see which one doesn't make you feel with your head. They have come a long with since the days of the TI AVIGO Back-lite Glow on green screen TouchPad. Now clarity for reading on these e-readers:
Pearl E has less gray, blacks are blacker, sharp crisper text seems to jump off the screen.