I get the arguments for Wilson, and if you took away my choice and assigned me him, or even Brady, I would still feel pretty confident (unless Brady was stuck with his 2019 weapons).
But the fact is that Mahomes has been in the league for two years, and I have yet to see any team figure him out. Aside from the games where he was hurt/limited, the only times the Chiefs have lost when he was on the field is when teams beat him in spite of his performance (eg, Pats last year). Closest any team has come to "solving" the KC offense was Detroit this season, and even there, he beat them with his legs.
Could the Niners be the ones who finally corral him? Sure, anything's possible, and they have the defense that could pull it off. I also wouldn't be shocked if they pulled off a Saints-stye 48-46 game where Jimmy G manages to go toe-to-toe with him. But if you ask me which QB is most likely to dominate in one game, smart money is on Mahomes.