Comparing GPAs has always been a bit of slippery slope as there is no set standard across the US -- this why many schools recalculate GPAs when they receive each applicant's transcripts. Even with a normalized GPA, there are dramatic differences course difficulty and grade distribution curves from school to school which limits the value of GPA as an assessment tool. As a result, SAs tend to look at class rank, the school profile, and assesses if the applicant is taking the most advanced classes that their school has to offer when reviewing academic performance.
Yes, it would be easier if applicants could but key factors into a formula to determine likelihood of an appointment (e.g. 1,500 SAT + 3.8 GPA + 3 sports + 1 club officer = appointment) but most there is no "easy button" when it comes to SA applications.
Good luck. Thank you for your willingness to serve.