1). Apps - every, with few exceptions, significant developer writes theirs apps for iOS first and if they have time, android. iOS has basically everyone on the same few platforms. Android has thousands of iterations to test. Also, way more revenue comes from iOS users cause android users illegally download or don't buy apps.
2). Security - android is way more open than iOS and anything goes. Security is an afterthought with android.
3). Ease of use - some people love to control everything with android and can find iOS limiting. While true, it also makes it easier to use for the non techies.
4). Reliability - apple devices have the lowest hardware failure rates of any major manufacturer.
5). Resale value - best in class.
6). Updates - want to compare the percent of users on ios6 vs jelly bean??