Paper phone
news.cnet.com
news.cnet.com
In the end, I'll take an Internet-enabled phone with a black-and-white screen and a 1 month battery life over a retina-display phone with 2 hours of battery life.
Also, good luck finding a phone where the screen has more effect on the battery than 3G connections.
All of them?
Try this: turn your phone's screen to max brightness and measure the battery life. Then do the same experiment with the screen off.
(Case study two: reading books on the Kindle vs. reading books on the iPad.)