if you are waitlisted at a school, how do they look at you the 2nd time you apply? how many people have been waitlisted twice in a row at the same school??
Sometimes it has to do with how late you applied the second time. If you are a late applicant, the chances are that you will be lower down on a waitlist. Other variables like the applicant pool that year, the interviewer you had, the people present on the admissions committee that day play some role. After interview, it's usually not GPA or MCAT alone that lead to a waitlist or rejection though, sadly, there is always an arbitrary component to the process.