With the GRE gaining profile and acceptance .... the decision between the two is tougher. There are lots of discussions and articles by experts around this at a general level, but the reality is this:
Schools will judge whether you provided the right test score based upon your unique application characteristics. ie. ultimately it's personal not statistical.
If you have any issues in your profile (over represented group, GPA, undergrad school, quant credentials, work experience quality, gaps, age etc), then a great GMAT score provides a stand-alone strong counterpoint to those weaknesses.
I think that programs are no longer ruling people out for taking the GRE but at the same time it's not providing a boost to their applications like a great GMAT score does.
My experience as a coach for both has been that it's easier to improve your GMAT score than your GRE score.
As I said, ultimately it's about your overall application profile, quant credentials and aptitude for each test that will answer the question of which one is right for you.
Happy to discuss more specifics (based on your profile) if it would help.