Hey,

Both the institutes are good for the preparation of the JEE M ains as well as for JEE Advanced . Both the institutes are giving top results in these exams from past few years. Both the institutes contain very experienced teachers.

But if you go by quality, then Allen is somewhat better than Akash. Their methodology of teaching is very nice. And also the study material that they provide is very nice for the JEE preparation.

For Maths, the key factor for good marks is solving as much problems as you can. So, solve each and every question that you can get from books, Dpp's, sheets, notes.

Hope it helps.