Uncharted 4 will win both easy.
I imagine sales will be lower than Halo 5 and it won't break 90 on Metacritic.
Edit: Looking at some more information on the matter, and I'm even more certain. Uncharted has been beating Gears in sales and scores since 2009. On top of that, Uncharted 4 looks awesome, Gears 4 looks meh. Naughty Dog is making Uncharted, a studio nobody has ever heard of is making Gears.
Bet with Adamblaziken:
I bet that on launch the Nintendo Switch will have no built in in-game voice chat. He bets that it will. The winner gets six months of avatar control over the other user.