This could simply be a function of sales. Android is now outselling iPhone by a two to one margin. Most of these sales are to people who have never had a smartphone before, and they're totally wowed by Android. So it would make sense that these users, when polled, would prefer another Android phone--after all, it's miles better than the dumb phone that they were previously using. They've never used an iPhone and don't see why they need one, especially given the higher price of the iPhone (most Android phones are dirt cheap, relatively speaking).
The Android installed base is 37% but only 31% of smartphone buyers want Android to be their next phone. The iPhone installed base is 27% but 30% of users want the iPhone to be their next phone. Whether or not this indicates the strength of Android, or the weakness of Android, depends on how many of those polled already own a smartphone. If most of the polled group don't own a smartphone at all, then it's pretty good for Android. If the polled group reflects current smartphone market share, then iPhone looks relatively strong, because that would indicate more existing Android owners want to move to the iPhone than vice-versa.
The Android installed base is 37% but only 31% of smartphone buyers want Android to be their next phone. The iPhone installed base is 27% but 30% of users want the iPhone to be their next phone. Whether or not this indicates the strength of Android, or the weakness of Android, depends on how many of those polled already own a smartphone. If most of the polled group don't own a smartphone at all, then it's pretty good for Android. If the polled group reflects current smartphone market share, then iPhone looks relatively strong, because that would indicate more existing Android owners want to move to the iPhone than vice-versa.