As a computer nerd who owns an iPhone 5 and a Galaxy S3, I can tell you that no matter what I do with my Galaxy, my iPhone is still easier to use, more simple to navigate, and is always more stable. It does everything I need it to.
The Galaxy. That's my fiddle phone. I can do anything I want with that phone, and it rarely complains. I can install different operating systems, I'm pretty sure I could dual boot if I wanted to. But so far every single thing I've done on my Galaxy that I couldn't do on my iPhone has been things only a nerd or geek would want to do. (Apart from use a proper Google Reader app, but that's no longer a problem with what's happening to it.)
So in the end of my 6 month review of the two phones, I've come to the conclusion (I came to it ages ago actually) that while the Galaxy is the superior phone in nearly every way, the iPhone is the phone that's going to let the average customer do everything they need to do with hardly any worries. (It also feels stronger.)
The average non-tech person who gets a smartphone doesn't want to dual boot it, they just want to use it. That's why Apple is so successful.
(And when some damn saleperson talked my grandmother into getting a cheap android phone, I felt like taking it to the shop and stuffing it up ....... never mind. That was made worse by most of her children using iPhones and iPads.)