Nexus 4, but you may not find one anymore for a price actually worth paying.
Android is fine. I was hesitant, but my wife just went out and bought me it. Now I have it, I wouldn't switch. Battery ok, not amazing, but no worse than other smartphones colleagues have. Screen quality great.
Nexus 5 due out any time now (ie October). You'd be lucky to get the Nexus4 anymore.
Sony phones, screen quality usually the thing that lets them down. Even their top-end one. Not Amoled/IPS IIRC I love the screen on the nexus 4.