I watched a very good pilot fly one day & noticed that he was using the pinch method so I asked him if that was for more control & if I should be doing that too. He told me it was just what felt natural to him when he first started learning how to fly so he stuck with it. I tried it but thumbs only feel more natural to me, so that was the end of it. I never gave it another thought. I do think your Instructor should let you do what feels more comfortable to you. I think if I were forced to learn using the pinch method I would have had a really hard time learning to fly(yes even harder than it allready was for me) So I agree with Ken, unless it is causing a specific problem with your training, I say use whatever feels right for you. Good luck.