The Gym Styles are more "interesting", with several different exercises to target all the muscle groups in different ways. GS's are great regular workouts for every week.
The S&H's are great for "breaking plateaus" and don't do quite as many different exercises as the GS's. You might even say they're a little "boring". Think of them as "meat and potatoes" workouts while GS's are the "apricot-glazed chicken with green beans almondine".
GS's are more the "cruisin' along the highway" workouts, while the S&H's are the "accelerating up the hills of Appalachia" workouts. In other words, they take a lot more effort. I don't do them as often as the GS's, but they give me a big boost when I do!