I've never had an iphone before, but am intrigued by them. My daughter is upgrading to the 5S tomorrow, so I thought I'd try out her old iphone 4 for awhile and see how I like it, and then maybe get a 5S or a 6 myself in a few months if iphone agrees with me. Realizing that I can't properly compare the experiences of using an older iphone 4 with a new 5S -- let alone a 6 -- what are the main differences in terms of features and use between the 4 and the 5S (other than size)? I don't want to unfairly judge the 5S based on a presumably inferior product in the 4, nor would I would I want to fall in love with some feature on the 4 only to realize the 5S got rid of it or something. Anyone have any thoughts on this?