All Android devices are not equal
TBH, I'm not sure the sales numbers can be used as a representation of peoples preference of Android vs iOS.
Personally I own an Iphone 4, and I love it, but there are Android phones that compete with the iPhone quite well on function and performance such as the Galaxy or Desire, while dirt cheap phones such as the ZTE Racer cannot really compare to either, and does not suggest a prefference for Android, merely a preference for a cheap smartphone.
I guess what I am trying to say is that a big part of the numbers are not comparable, a similar comparison would be android tablet sales compared to the ipad. I dare say that there are likely more android tablets manufactured than the ipad, they are everywhere, yet with only a few exceptions, they cannot really be considered compitition.
To be honest, I have to wonder if this sort of comparison may ultimately damage Android, since it seems to suggest that all Android phones are equal, and for a person who buys a cheap android device, it may be that the first device will be the last.