Small nitpick: dual core devices were most certainly WP8 devices, since WP7 did not support multicore devices
When Windows Phone7 came out, my friend had a budget WindowsPhone7 with a single core that outperformed dual-core Android at the time when it came to being a phone. The WP7 was a lot less laggy. Then when I got my first Windows Phone8 it was dual-core instead of the then Android quad-cores and it out performed those as well in anecdotal comparisons of mine.