OK my 2¢...
IMHO the most important thing is the software, not the hardware. And plain vanilla Android is far better than Android gummed up by overlays like Sense or Touchwiz, which are deeply ingrained into the OS.
Pure Android runs faster and smoother than Android burdened by manufacturer customization, which are bloated, actually, and often buggy. Sorry, but they are, face it. If you don't like lag, if you do like smooth, and if you want fast OS updates, then you definitely want pure Android.
Fortunately, you have some fine hardware available running vanilla Android. The Moto units that have been mentioned. The new Nexus devices should be very nice. And the Nexus 6, at the price you can buy it for right now is a terrific deal, a buttery-smooth running premium device at a mid-range price. My wife and I both have one. BTW I think the camera is not bad, maybe has gotten an undeserved reputation. Kinda weak in low light yes, but good otherwise. We've taken lotsa good looking photos with ours.
Anyway, I don't think you would go wrong with any of those. Just pick one with the price and features that best suits your needs.
Android since v1.0. Linux since 2001