I go to both fairs every year, and I guess I always think of them as, well... fairs. Pony rides, deep-fried oreos, barnyard smells. Not a place I want to see a rock band play. Maybe it is just my mindset.
Yes, Puyallup Fair (or is in the WA State Fair now?) has more country acts. And I have seen a show at neither. Unless you count Gallagher.