http://www.anandtech.com/show/6914/samsung-galaxy-s-4-review...
No Lumia on there but I think that matches up with the general btty life rating for iphones. Some nokias in this listing:
http://www.anandtech.com/bench/Smartphone11/349
"CPU and GPU for the end user isn't important."
It certainly can be for certain apps.
"WP7/8 have always been buttery smooth when compared to iOS and Android devices with better hardware."
I'm not sure why you've lumped iOS with famously jittery Android (at least historically, 4.2 seems to have solved lag) since iOS is usually cited as the standard for smooth interface as in this initial WP 7 review from Josh Topolsky: "probably the most accurate and nuanced touch response this side of iOS4."
That's where iPhone seems to excel. On a fresh install of Android, using just one built in app, it seems fine. But eventually the phone fills up with stuff that seems to drain it. Not sure how Windows Phone fares on that front.
However, Android gives you tools to see which apps are using the most battery, and you can uninstall them if they're a problem.
Recently I noticed much worse battery life on my nexus 4, opened up the battery stats, and saw 30% of my battery usage was the consequence of a messaging app I don't use, deleted it, and got back to normal.
It looks like the iPhone and 920 battery life are both pretty abysmal http://blogs.which.co.uk/technology/phones-3/best-phone-batt...
CPU and GPU for the end user isn't important. What is important is the perf of the UI, which WP7/8 have always been buttery smooth when compared to iOS and Android devices with better hardware.
I'd also say Nokia is very closely behind Apple in build quality if not on par. And their form factors have been great as well.
iPhone/iOS definitely has a better ecosystem, but the apps on WP8 are getting better.