Well OP,i guess you are familier with androids very much..so....,always,always remember before buying an iPhone that iPhone's eco-system is closed,and that when people say "customizability",It doesn't only mean the fancy themes or so,It means a closed experience,You would be doing things the Apple's way,so it is not a "feature-ful" experience,but yes it is a way most people choose over android's cause it just works for them...And also iOS appstore is way way way ahead than Google's,from the app design to the consistant UI to the wealth of features...So the Apps do close the little "preference" gap or "feature-gap" but still,it is quite like "Apple's way" and you cannot,tinker with them (Here,tinker is different the word customization,in general sense of the word"...
I would give you an example..like I wanted the reminders app to display reminders on Lockscreen/Notification center all the time,to have sort of a glance-view of them,but iOS doesn't allow that,not even with appstore's app,so I can't have that option,the reminders only display in the NC few hours before the task...So this is limitation..and it is not "strictly" related to "Customization"...So do watchout for it,if you are fine with those things,then it means iPhone would prove to be a practical phone for you and not just looks,If not,then go for Moto-X...