I look at performances against common opponents - not in terms of metrics, but for a general feel.
We could have beat the Niners. The game was closer than the score indicated. Now look at what the Niners did to the Cowboys. Coach Big Mike and Zac are a match made in limbo. The scheme and demands of the position are slightly out of reach for the QB. The Niners O took it to the Cowboys and beat them physically, and the Niners D threwthe Cowboys Oaround like rag dolls, and not without the sneaky-dirt that's there to be seen in you keep an eye out for it.
The Rams played tough against the Eagles. Given my logic, the Eagles and niners would make quite a football game, and both teams at close to full strength, the Eagles would win it decisively.