Previous two posters pointed out what I was about to post. Same number of pixels on different size screens use different amounts of power due to the different sizes of pixels. The Droid Ultra's pixels are larger than the Moto X's pixels; consequently, each pixel uses more power. The difference between a 4.7" and a 5" screen's pixels size will be very small and the power usage difference will be small, but the larger screen will use more power.
Originally Posted by Sandroidfan
I'm also puzzled that Ultra has more battery life as listed on Verizon site. Screen and battery size don't make sense for that.
It's the magic of the Verizon Droid! lol It's simply Verizon fudging the numbers and taking advantage of the very vague description of "mixed usage". They wanted the appearance that the Droid line was slightly better in battery life so they could use it as a selling point to the consumers that don't know better. I guarantee the Moto X will outlast the Droid Ultra by over an hour given the same mixed usage rules. OR an extra 15 minutes of screen on time.
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