I don't know how much stock you put in PFF (frankly I don't know how much stock I put it in either). This season they have Rapp and Hamlin graded as 66.3 and 61.4. They have Reid and Cook graded as 66.2 and 59.2. I'm sure Reid and Cook are given more difficult assignments which puts their grades on a higher curve. Still it is not a stark difference IMO. Since safety and LB are devalued positions, there would need to be a massive talent gap there for me to give anything more than a slight advantage to either side.
The post I responded to said the Chiefs defense is "much much more talented" than the Bills defense. I don't agree with that characterization. They have a 1 of 1 talent which gives them a distinct advantage automatically. Other than him I would say the rest of the units are of fairly even talent. If you took Chris Jones away and asked every defensive coach which roster they'd rather have I'm not sure either side would win in a rout. Spagnuolo's scheme is the other distinct advantage that they have IMO. His blitz packages have given our offense fits. I can't remember a time that we did the same to them.