I love the Nook glow light. It is small, lightweight, and the battery lasts for 2 to 4 books! I much prefer no backlight but will turn it on occasionally. I prefer the Nook since I read mostly ePub either from the library or a free download (at bookbub you can sign up for a daily email for books by interest area available for free to $2.99.)
I tried reading on the Nexus 7 and prefer the Nook. I replaced a first edition Nook with the Glowlight. One thing I like about the new version is the ability to get online for B&N downloads from campground WIFI where you must enter login info.
I just got an iPad which is fine for web surfing and email but feels big and heavy for reading, but I did install both Overdrive and Kindle apps.