E-Reader Review: A Little Night Reading With Light-Up Devices - WSJ.com

Final paragraphs of an enlightening review

"As is expected, the battery life for both devices is affected by the lights, but is still very good. Amazon estimates the Kindle Paperwhite will last eight weeks with its light on. Barnes & Noble says the Nook Simple Touch with GlowLight will last for a month with its light on and two months with the light off. Both companies tested battery life for a half-hour of daily reading with Wi-Fi off.
If you still can't decide, some of Amazon's extra features may sell you. Certain titles from the bookselling giant include a feature called X-ray, which displays extra details about the book. And the Kindle Paperwhite can receive library books via Wi-Fi, while the Nook uses a clumsy transferring technique that requires a USB cord."

E-Reader Review: A Little Night Reading With Light-Up Devices - WSJ.com