"While the RIM's Blackberry OS holds the crown for United States smartphone dominance, Apple's iPhone ranks second, and Android is quickly rising in the ranks. As Google's Android mobile platform continues to grow in popularity, so does the range of alluring smartphone hardware that runs it, which with every passing iteration takes further aim on the iPhone juggernaut."
can't go wrong with either imo. I prefer android due to openness but really its just preference.