Yes Allen is good. But I will recommend few points to be kept in mind while taking admission in any coaching institute-
See average results. Allen has highest number of students enrolling every year, so they show a huge number of students qualifying. On the other hand resonance and vibrant have good average results.
Dont go with the number of toppers showing the coaching institutes. See the number of students of regular classroom course student and students taking DLP. You will understand the differences.
See the number of students qualifying from that particular branch of coaching institutes in which you will be taking admission. If fiitjee is showing the number of students qualified is X. Then X is the total no of students qualified from all center all over india not only South Delhi fiitjee branch which is famous among all fiitjee centers. Same with Allen and resonance.