well iv had both, the iphones market place is better imo, the apps are better quality , and the games are better quality. but i personally hate itunes its self. for the pure cost of the music, 150 for a song? come on, android apps, are in the most case copies of the orginal apps that iphone had, some are awesome, some blow ass. and some are just pointless to point where you think to yourself, wtf is this ? , but all in all i personally like the way android runs,looks, and performs. the iphone os just doesnt measure up anymore. its kind of outdated. when apple comes out with something "new" other phones have had it forever, retna display? ok cool, super amoled samsung screen was out first an in my opinion looks better and more crisp. also the screen is so damn small now that i have had a 4.3 and 4.0 screen. camera wise, the iphone still sucks, my nexus s 4g takes awesome pics. wayyyyy better quality pics than my friends iphone 4.
that is just my take on it since i have had both.