There are several "hard" decision points to talk about first and then it gets fuzzy.
(By the way, I host a monthly workshop on this topic. I just taught it last night and there was someone in there named John. But that's a pretty common name... still, I'm wondering whether it was you! Also, FYI, the next one won't be until early January; we're skipping the Dec one because - holidays, etc.)
First, you need to check the websites of the schools to which you plan to apply. The vast majority of schools accept the GRE but some don't; if you want to apply somewhere that requires the GMAT...you'll be taking the GMAT!
In addition, some schools that accept the GRE publicly state that they prefer the GMAT. That one's a little fuzzier, since they do still accept the GRE - but, if you're on the fence, that should probably push you towards the GMAT.
Third, are you planning to go into banking or consulting after b-school? If so, I strongly recommend taking the GMAT. We have had students who are already in b-school taking our GMAT classes because they were told by top-firm recruiters that they needed a GMAT score (and they had taken the GRE).
If none of those factors knocks out the GRE for you, then you have a decision to make.
First, I'd call your quant about equal for the two tests. The Q percentiles have skewed down on the GMAT because of the large number of international test takers in recent years. That same GMAT Q score was about 15 percentile points higher 10 years ago. In general, if you're aiming for a top-10 school, then Q45 is at the lower end of what is typically considered "good enough".
[NOTE: "good enough" does not mean "you will get in," of course. Nor does it mean that they won't let in some people with a lower score. But generally speaking Q45 to Q47 demonstrates that you can handle the quant work at that top school.]
For the above reason, schools also seem to want to see somewhat higher quant percentiles on the GRE. (I say "seem" because most schools haven't published average or median GRE scores yet.)
Anyway, so factor in that your quant starting point is actually pretty similar.
Next, do you think you're better at learning grammar (GMAT) or vocab (GRE)? (Factor in your gut feel AND how you did on these topics in school.)
Are you better at geometry? data interpretation? --> GRE
Are you better at story problems? number sense / number logic? --> GMAT
What do you think about all of that? If you're leaning one way, go for it. If you're still on the fence, I'd go with GMAT as the tie-break.
(Oh: and my expertise is not in the broader admissions area, so I don't know whether they'd look at your undergrad degree and wonder why you took GRE vs. GMAT. Ask that question in the Ask An Admissions Consultant folder in our forums.
