Well, they may not be unstoppable juggernauts without their respective kryptonites (Seattle sometimes falters on the road like the Saints; Peyton chokes on the biggest stages), but I think it's safe to say that both are good.
When the playoffs come around, only SF and Carolina have enough on both sides of the ball to beat sea in the nfc playoffs IMO. Phi could be interesting and Dallas will slip like they do every year.