A:Answer29 minutes. just be aware and quickly restart the recording once it hits 29 minutes. It doesn't matter the size of the memory card, it only goes to 29 minutes which I believe most DSLRs is around that length....
A:AnswerStick with a GoPro. The Canon t6i is way to big and bulky for the mountain side and would be a huge financial loss if you dropped it in the snow. As for handling temperature... I'd ask Canon directly. In my opinion, quality of the shot WOULD be better, but at a pretty great risk.
A:AnswerThe major difference is that Canon EOS T6i is a DSLR camera and provides 24 MP resolution whereas G7X Mark II is a fixed lens compact camera and provides 20 MP resolution.