"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."
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."
http://www.engadget.com/2010/10/20/windows-phone-7-review/