It's close, but I give the edge to the Patriots I think.
I feel like the Chiefs were the biggest threat to the Patriots honestly. Their offense combined extreme talent with extreme unpredictability - even when your defense "won" its matchups, Mahomes would often make a big play anyway. He can make throws out of the pocket & on the move effortlessly, and the Chiefs have a lot of extreme athletic ability among their receiving weapons. It's extremely hard to plan for that, and past a certain point even Belichick can't just scheme away the other guy being way faster than you. It's almost like they were built to vex the Patriots defense specifically.
Goff by contrast makes virtually all his plays within the offensive system - by following the rules, staying inside the lines, making simple "if A throw here, if B throw there" reads, with a lot of motion and formation variation to create the illusion of complexity around what are simple concepts of "fake pass then run"/"fake run then pass."
And these are all things that Belichick can analyze and develop counters for. Goff is still relatively inexperienced and has to be spoon-fed a lot of reads by his coach before the play clock hits 00:15, and that just seems like something Belichick can exploit.
On defense the Rams are better than the Chiefs, but a lot less than they should be (like #20 in scoring or something), and all year they stunk against the run - a strength for this year's Patriots team. They have a single amazing DT... but their pass rush was far weaker than the Chiefs all season, and the Pats OL shut the Chiefs rush down completely. Every year people predict X super pass rusher is going to kill Brady, and it keeps not happening outside 2013 (a perfect storm of OL injuries meeting Von Miller & Ware) and 2007 against a Giants team with a simply monstrous front 7. The Rams are not on the level of either of those defenses - outside of Donald they're a bunch of big names not quite playing up to their name recognition.
