What is the quality of an online course from Aakash Institute? How does it compare to their offline classes in terms of advantages and disadvantages?

Online course of Aakash Institute does provide you with adequate study material and lectures, but I would still prefer online classes over it.

Obviously, one can concentrate better and be more sincere in offline classes. The doubt solving, I think is more effective offline. However, that is debatable.

I think offline classes are best when your residence is close to the center and shifting to a PG or hostel isn't the most convenient solution.

Online classes can provide you mobility in terms of where you are taking classes from. If there isn't a center in your area, I suggest go with online but if there is one, offline is the best.