I've had memberships at GT and JamPlay over the past few years.

GT is better...by far. Here's why:
1) Curriculum is organized much better.

2) Teaching methods and explanations are consistent with curriculum. For example, watch Lisa McCormick's "Focus: Chords." The progression of the classes is well organized and explanations/demonstrations are top-notch.

3) GT offers areas of focus while JP is more instructor-focus. For example, as a novice player, I started with JP. I searched the instructors, selected one and stuck with him for six months. Good instructor...but the training was all over the place. I couldn't track my progression.
- GT is superior because it's easier to understand - and follow - the progression of the classes. Ultimately, the organization of GT is a competitive advantage.

Finally - here's another plug for Lisa (note: I never met her) - is an outstanding teacher. Her explanations are thorough and interesting. She applies concepts to real-time playing. And, here's the best for me, I've evolved into a much better guitar player because of her classes.

GT is the best value for the money for me.