Great written, however your comparison is not fair at the first place!
As far as look (interior and exterior), there is no doubt 6er is much better than Panamera (IMO). Regarding to handling, engine and power you have to compare GTS with 6GC Xdrive since both are AWD beside the same power. You also can compare RWD Panamera s with RWD 6GC then you will see that 6GC beats Panamera easily.
In addition, Panamera turbo and turbo s will be the competitor of M6GC
BTW, I like Porsche and respect that great German engineering and quality