That's a great question. Currently I'm using a Galaxy Note 3 and love it no complaints whatsoever. And after trying out the Note 4 at Best Buy it seems liken obvious choice aside from the fact that the broken link in my Apple set up is my love for Android phone. At home I use a MacBook Pro and Apple TV. At work and on the go, I use the Note and iPad. I originally left the iPhone in the first place because I wanted a bigger display and felt like Android was mature enough. Keep in mind I switch back with the S3 and have owned several Android phones since then. However curiously, I REALLY like stock vanilla Android. However my experience with the Nexus 4 was very unpleasant. Horrible camera, no LTE, and the phone would overheard even just charging. Forget about regular use, this thing would get HOT! However it looks like Google has finally solved things with the Nexus 6.
As to which phone I'm leading towards, I'd have to say honestly the iPhone 6 Plus. I've been with Android for the past few years and I really want to give the iPhone another go. I feel like the continuity between my Apple products might be worth the switch. Granted I haven't been looking too hard, if I can find a 6 Plus in stock, I'll probably pull the trigger.