Uday, AIIMS released its result in the form of percentiles and NEET releases its result in the form of score. Now AIIMS MBBS was held for 200 marks and NEET is conducted for 720 marks. Considering all these factors, you should score atleast 600 and above even with OBC reservation. This is because AIIMS seats are filled through All India Quota which means every eligible Candidate can claim stake for a seat in AIIMS. So any score less than 600, might put you in a tight spot.