Hey,

Coaching institutes are there for helping only. None of the coaching institutes can assure any result as it depends on the students ability, attitude, aptitude and more importantly hard work.

There is little to choose between the two institutes - if you are planning to go to Kota you can plan for Allen, otherwise go for the other one. Don’t depend on the institutes for core subject clarifications - use them for organised notes, periodic tests and test series.

If you have already taken one year in any of the medical specific coaching institutes (say Allen), instead of going again to one of them, you can join a JEE coaching institute. Bit counter-intuitive, but can work if you are relatively weak in physics and chemistry.

Study biology on your own and with the previous year notes, physics and chemistry in a JEE coaching institute (as medical coaching institutes tend to focus on Biology more) .

Ultimately you are your best judge. 

Hope this helps.