I was in the droppers batch in allen. What I did not like there was that they take test every 3 weeks. In that 3 weeks students get a damn high pressure of scoring a good mark and teachers there say if you can not score more than 30% , your dream of getting into IIT will be a dream. On the other hand, Resonance is better. It takes test evry week for 2 chapters. It is the best way to revise your studies. If you are going to kota for IIT classes, trust me resonance is the best institute. Allen is also good but the most important factor is self study. Wherever you go you have to study to acheive