I picked the 49ers before the season and before the playoffs. The 49ers, by every advanced metric, were the better team this season. I am a 49er fan and so even if none of that was true, I would still pick the 49ers in this spot - it's the Super Bowl, I'm picking my team - however, I pick this game every year and unless a significant countervailing issue makes the season totals not the single best predictor (variance is more important than everything, "any given Sunday" and whatnot; you throw the Bears into this game and 4 times out of 10 they win, don't overrate ability to predict the outcome of an NFL game), I pick the team who had the best season. No - a couple of playoff games are not a significant countervailing issue - if Mahomes missed half the season or Trent Williams wasn't playing Sunday, that's what would be needed to buck the season long results.
The 49ers run the ball - the Chiefs don't stop the run.
The Chiefs one skill position weapon is the tight end - the 49ers shut down tight ends.
The Chiefs have an offensive tackle problem and Nick Bosa puts more pressure on the QB than almost any other pass rusher in football.
If you're picking the Chiefs, and a lot of folks are, it rests on the distance between the quarterbacks and thats a reasonable call. A different way to pick this game would just be to pick the better QB given the wildly outsized impact on winning that position has - Mahomes is a two time champion headed to the Hall of Fame and Purdy was the last pick in the draft and there were advanced analysts calling for him to be replaced by Sam Darnold before the 4th quarter of the divisional playoff win over the Packers.
If I had Mahomes on my side, I'd pick him too.
But instead - I have everything else.
49ers 26
Chiefs 23
I'm going to throw in some props I like, I'll update this as it strikes me:
Eli Mitchell over 4.5 rushing/receiving yrds
Deebo Samuel under 2.5 carries
Brandon Aiyuk over 4.5 receptions
Kyle Juszczyk over 4.5 yds receiving