The extreme disparity between Pandora and iTunes Radio contradicts any competitive framework that pits the two services head-to-head. But the deck is stacked: iTunes Radio is available only on Apple phones, while Pandora plays on both Apple and Android smartphone platforms. The numbers released by NPD to the press do not specify platform use in the sample.
YouTube ranked highly in this survey, but also might suffer a platform disadvantage when it comes to smartphones. The YouTube app is available on all devices, but performs better on tablets and computers — partly because of larger screen size favoring video, and also because of bandwidth constraints that might discourage streaming video through phones.