I see benefits to both the S&H and the GS workouts. When I want to get a good pump in a particular body part, S&H fits the bill, but when I want to really tackle a body part from all angles, I throw in GS.
What I've been doing lately is mixing and matching, and it's giving me great results. For example, I did PUB the other day, but only the chest, shoulders, and triceps work. Then I threw in GS: Chest, Shoulders, and Tris and did the Supersets premix, skipping over the pushups (because I'm just not ready for those, yet). I did the same thing for back and biceps a couple of days later. What an incredible combination of strength work! I was actually thinking about how I would like to combine my S&H series with GS, as well, to really exhaust the muscles for an optimum burn.
The reason I like GS so much is because Cathe incorporates a lot of unique weight work. I mean, I just love those lying down, cross-the-body, triceps extensions. And, all the different shoulder exercises she incorporates, plus the incline bench presses just really hit the muscles in new and different ways! I feel like each body part gets hit and hit, and then hit again from yet another angle with GS...meaning that when she does chest, she hits it from every possible angle (and when she's finished with that, she pulls out the resistance band for a bonus burn that really sculpts the muscle) so that by the time chest is done, no muscle has been excluded and has been hit from all directions to maximize performance.
S&H or GS? This is a tough one, but I'd have to go for GS first, then S&H second.