I am in class 11 and I am studying in aakash institute for IIT-JEE preparation but I have my classmates and friends accompanying with me in aakash and many of them studying in other Institutes like narayana, fit-jee, Vidyamandir, etc.and I find no difference in all of the institutes, it all depends on the hardwork you do how much consistent you are towards your are towards your studies so I think you can join any of these institutes according to your wish and will. So I hope this information helped you.
Thank you so much guys.