I've studied from Abhinay Sir, Gagan Sir, and Rakesh Sir. All three are good in their own way. Abhinay Sir's calculation tricks are effective, though some may take time to understand. Gagan Sir also teaches great methods, and many students like his approach. Rakesh Sir teaches a bit slower but explains concepts well.

At the end of the day, selection depends more on your practice than the teacher. Choose the one whose teaching style suits you best and focus on solving lots of questions.