One-on-one instruction is generally better. The instructor can pick out the weak points of your game and adjust your training accordingly. It's difficult to do that in large classes with students who have varying skill levels. Also, if you can find an instructor who gives lessons in a private place, such as his home, you won't have interruptions from other people and you and your instructor can concentrate on your game. And you won't be paying for lessons for people who are nearby listening in to your session! I'm not saying your can't get good help out of group lessons but, personally, I prefer individual classes as I can concentrate on the student and his issues and the student can concentrate on my help. For example, if you can't draw your ball, I can fix that in 15 minutes. It's difficult to do that with a large number of people in a class. Also, you will find that individual lessons are no more costly than group ones and you are not committed to a two day session if you find the class is really not addressing your needs.