The XAT score acceptance for the selection amounts to about 60%, and if one includes the other essentials checked as part of the profile like Essays, GK, Academics, Work Experience, etc; that comes to 15%. The GD/PI round amounts to 25%. However, the bottom 10% score received in GD/PI rounds may not be considered for final selection.
If you score a 97 percentile and someone scores a 99 percentile then clearly the topper with the 60% XAT score will sail through with ease. When evaluated further, the 97 percentile means that that your XAT score is about 45% and the other students are 60%, so there is a margin of 15%, hence the advantage of the topper is clearly visible by the 9% rise.
It will finally come down to the GDPI score which has a 25% weightage. The 9% advantage of the topper student will be a challenge to overcome, and for that, you must excel in this round because the topper, most probably, will prepare averagely for the interview.
All the top B-schools, except FMS, emphasize the PI score during the selection process so that even the top candidates get rejected based on their profiles and scores.