When I get my new phone in January I want one of the above. However I am wondering which one is better. I have already bought a lot of music and apps for iPhone as my brother and dad also have iOS devices. However I briefly owned a nexus 7 and bought many apps on android as well. Just wondering which is better. I can only upgrade to an iPhone 4/4S or Samsung Galaxy S2.

PLEASE HELP. I will choose a best answer!