You'll see this debate on here a lot so utilize the search function.
Regardless, here is my take:
When I got into college I was really surprised at the weight of the MCAT. I spent a lot of time keeping my GPA high until the difference between a 3.6 and a 3.9 could be made up by getting a couple more questions right on the MCAT. Why is this so? The MCAT is the SINGLE most important COMPARATIVE tool adcoms use when assessing the academic POTENTIAL of students. This is because, as I'm sure you realize, GPAs are relative.
Generally:
MCAT:
**Note, tiers is arbitrary, my definition is:
Top 30 research US News-Tier 1
Top 40-80: mid-tier
Any of the rest: low tier
24-26: Will keep you out of American MD schools. I'm sure acceptances aren't unheard of so feel feel to gamble.
27-29: Will not knock you out of the running but will signicantly hurt you. See 27-29 MCAT forum for evidence of this. Apply to all low tiers and maybe a mid-tier or two as a reach. Also, make sure you apply DO as well.
30-32: Decent score, 32's the national median for ACCEPTED students. Apply to low tier and mid tier MDs. Also, apply to state high tiers. Apply to maybe one DO just in case especially if the GPA is low.
33-35: Excellent score. 34+ and you're in the top 10% of all test takers. Apply to state and OOS mid-tier schools, some low tiers as safeties. State low tiers should be your ultimate safety. Apply to in state higher tiers if applicable and maybe an out of state high tier as a reach.. Only apply DO if you're c/sGPA is lower than 3.5.
36+: From here on out the issue becomes getting more questions 1-2 right per point. Apply to any school in the US you want. If your GPA is below 3.4 apply to some DOs just in case.
40+: You literally go up a point if you were change an additional question. Apply to any school in the US you want. If your GPA is below 3.4 apply to some DOs just in case.
See how I used MCAT? I used that instead of GPA to tell people what schools to apply to. This should make an impression on how important it is to get a good score!
Now, what about GPA?
Now let's talk about GPA importance. Students who had 27-29 on their MCATs has a low 40% chance of getting into medical school if their GPA was 3.4-3.59. Now if they had a 3.8-4.0 GPA that chance increased to a mid-60% chance. See, in contrast to the MCAT which is the best "inter-student" indicator of academic POTENTIAL, the GPA is a "intra-student indicator of how HARD-WORKING a student is". Therefore, if you got your heartbroken with a 27-29 MCAT, if you have a 3.9 GPA then I would say you have a chance. Therefore, the high GPA will let universities know you have the heart and work ethic and will be forgiving if they like you but it they won't compare it so other people's GPAs.