Reading this thread with some interest - and the lack of a definitive answer reflects my own thinking on this.
I've got an iPhone 4 and, three years down the line, I've not found a compelling reason to 'upgrade' any further with a newer Apple product. Its running the current iOS and does what I need it to do with a minimum of fuss - albeit in a bland kinda way. Add to that my experience over the past year with a Nexus 7, running the 'naked' Android experience. Its given me a good starter point from which to experience that OS - and I've got it syncing with all the same items that my iPhone uses and am using most of the same apps, so no significant loss of functionality.
That said, both OSs have 'features' that drive me nuts (and most are OS-embedded apps) and I know I'll miss iMessage and the basic, if efficient, Photos app in iOS (Android's 'Photos' or 'Gallery' handling of sub-folders within a larger folder - such as a sub-folder 'Bob's Birthday' in the folder '2012' - terrible, and no app found that improves upon iOS app), while I've yet to find an Android app that favourably matches (or betters) that used on an iPhone. Most Google apps wished for available on the iPhone, with the advantage which ones to choose to load, unlike on Android.
I certainly get that Samsung has a whack of their own apps on the Note that expand functionality well beyond the naked Android experience and though my in-store experience with them show their use to be at times convoluted - but its that functionality (oh, and did I mention the huge screen) that draws me to consider a move to the Note 3. But both devices and their OSs (as noted by other' postings above) have their pros and cons - and I wish I could say I was inspired by one over the other. And I'm not sure that a (rumoured) screen size increase on the iPhone 6 - eventually - is worth waiting on. Apple is running at least a year behind the curve hardware-wise - and the OS is 7 years old.
Conundrums.