I am a current iPhone 4 user looking to upgrade to an Android. I'm simply fed up with Apple for many reasons, I'm sure most of you know them. Among my particular complaints; small screen, no customization, and lackluster Google services integration. I am an AT&T customer in the USA. My budget is $400, although my 2-year contract is up, so applicable discounts are available.
Screen size, screen quality, 720p HD, and very high brightness is crucially important. Watching YouTube, browsing the web and even playing games on my iPhone is a terrible experience because of the size and resolution, despite the quality of the screen. If I can find something that makes these things enjoyable on a phone, I will be a very happy person. I cannot emphasize the importance of the screen enough, it is the most significant thing on any spec sheet to me. Of course, some great performance so I can play all the latest games and future-proof is secondarily salient. I'm not too worried about software, as long as I can load other less-bloated, nicer-looking ROMs onto it, it won't be a problem. LTE, though not essential by any means, would be convenient as I am covered well where I live. Either good internal storage (~32GB+) or a MicroSD card slot would fulfill my needs there. I do really like the design of the iPhone 5, it's way down the list obviously but some nice aesthetics and ergonomics would be sweet. I'm not sure if I have an outstanding need for battery life -- If it's decent, I'll be happy, and if it's great, I'm ecstatic.
I did consider the Nexus 7 and the Nexus 10, though I would rather concatenate my tablet and phone into 1 device. Still, I am very much open to advice.