And this suggests that "Demographically, Android phones are especially common among young adults and African-Americans, while iPhones and Blackberry devices are most prevalent among college graduates and the financially well-off."
Blackberry seems to win, probably through being an early provider of group messaging to a young, early-adopter demographic on one side and a business staple on the other and the twin lock-ins that provides.
Though note that "white people" are about 10-15 years older than other categories on average so white, middle-aged, and affluent kind of go together and can be hard to tease apart.
Recently, I've seen a lot more high end Android devices, but a few of my friends have gone back to flip phones surprisingly.