One on one on be very beneficial, you have someone you can ask questions. It may take a while to find the instructor that works for you. Some people are good guitar players, who teach, but are not good teachers. Don't feel obliged to stay with an instructor. I finally found a great theory instructor, who took my playing, and understanding to a different level. Yes, I think it can be very beneficial, but you may have to try a few different instructors until you find the one that works for you.