Hi Andre4,
I can tell you that, from the perspective of a GMAT instructor, I can show students so much more through an online course approach than I can through an in-person session. Most of my prior GMAT in-person tutoring sessions require me to think through questions - then formulate a best way to explain the solution -- and then gauge the student's understanding along the way. The student often takes a few minutes to look at a question or a passage. Every minute counts when students are paying me by the hour -- and an hour goes by quick.
But through my online course, students are not paying by the hour. They are also not paying for the time when they themselves are thinking about a question and have not yet figured out what question to ask me. In short, it's a lot more cost effective and efficient --- and so students are generally much happier for getting more and paying less.
That said, some students need that in-person interaction. So it really does depend on your learning style.
Regardless, we encourage you to learn more about some of our students' journeys:
www.gmatpill.com/testimonials