If there is an interview for you it is during in the processing period. The VO will decide to go further only after interview. The time taken between interview and medical depends to visa office. If you go through the threads about New Delhi processing in this forum you will get an idea while comparing the cases or go to the trackitt site.
Actually i want to choose New Delhi because I dont have the notarised copy of visa page of my passport to prove that I am a legal resident of UAE and sending the same to India will take time so therefore wanna finish off things by choosing New Delhi VO.