G had to do it. Compare Windows Phone 8 to Android - Dual core WP8 phones were better or equal in performance compared to quad core Androids! Had compared Lumia920 with SGS3 few months back.
On every single one of them, the brush ends up lagging ridiculously far behind my finger even with quite slow strokes, while on the FirefoxOS phone, I hardly noticed the lag unless I did fast sweeps or used a stylus (there is lag there but usually small enough that if using a finger, my fingertip obscures it)