Competitiveness is based on a few things for me:
It's based on the ratio of the number of applicants to the number of accepted applicants. If school A receives 1000 completed applications, school B receives 500 completed applications, and both schools only accept 100 students, then school A is more competitive because more people are vying for the same amount of spots as school B.
However, you do have to consider the average GPA and PCAT when considering this. A high average GPA generally reflects higher competitiveness, though a school with a lower average entering GPA could mean that the school is looking for a more well-rounded individual and therefore look harder at other factors. Also, it depends if you are an in-state applicant or not. Some schools really slant their pool for in-state students. That makes the competition easier for in-state students, but a lot more difficult for out-of-state students.