Patrick Mahomes had won 3 Super Bowls, and played in 4 overall through his career because he's capable of doing and excelling in a lot of the "little things" during games and post-season games so well like converting key 3rd and 4th down plays late in-games and like on 4th and 1 and elevating your skill set to another level even when your offense isn't operating at 110% efficiency, or scoring 40 points like most analysts or experts believe you're capable of. This was, as you and others have pointed out, mostly a great defensive showcase and battle in the trenches, and yet Mahomes still found a way to throw for over 350 yards and 2 TD's, and ran for 66 yards. He excelled and was so dominant at doing the little things his team needed to him to be capable of reaching, which finally lead to the game-winning score in OT.
Purdy is a very good game-manager and he has shown some flashes here and there, like vs. Detroit in the NFCCG, of putting the team on his back and finding a way to win a close game, albeit helped and assisted by some questionable, idiotic calls made by Lions HC Dan Campbell. But, you have to show consistency in this regard and Purdy hasnt been around long enough or is unable to ultra-clutch in key moments in big games. He's got an excellent supporting cast and as long as they remain (CDMC, Kittle, Samuel, Aiyuk, good shout defense) he'll continue to look like a perennial Pro-Bowl until he plays that great, excellent defense who'll contain all of his little toys and reveal him to be what he truly is.