With regard to the GMAT, raw intellectual horsepower helps, but it is not everything. In this blog series, Manhattan Prep‘s Stacey Koprince teaches you how to perform at your best on test day by using some common sense.
Many business schools, including Stanford, Harvard, and Wharton, accept either the GMAT or the GRE. I have spoken with a couple of admissions officers about this topic, as well as several students who have had their own conversations with admissions officers about which test to take.
The general consensus seems to be that taking the GRE instead of the GMAT confers no major disadvantage, but some schools do (as we suspected) discount the GRE quant score a bit because they feel that the GMAT quant is more challenging. (And I think they are right about that.)
No one would discuss specifics, but here are some things I inferred. First, the discount is not enormous—my guess is that it is on the order of perhaps five to ten percentile points. If you, for whatever reason, find the GRE quant much easier than the GMAT quant, then it still might be to your advantage to take the GRE.
Second, so far, I have only heard top schools acknowledge doing this. Certainly, any schools could discount the GRE quant; my guess, though, is that everyone else is not as concerned about the small differences in score/difficulty level between the two tests. The top schools receive so many applications that choosing among all of the highly qualified candidates is extremely difficult, so they are even more concerned about making an apples-to-apples comparison (as much as they can).
Finally, no one expressed any concern about the verbal portion of the GRE; the schools seem to view the two tests as equally challenging in this area. (And, again, I agree with this assessment.) The GRE and GMAT do test somewhat different verbal skills, but vocabulary (GRE) is just as important as grammar (GMAT) in business communication, so neither test has an edge here. (Both tests address meaning in their vocabulary- and grammar-based verbal questions.)
What does this mean? If you are applying to a top school, you should have a slight preference for the GMAT over the GRE, but if you are really struggling with GMAT quant, then try a GRE practice test (under 100% official conditions, please!). If you find the GRE quant a lot easier (enough that you can score at least ten percentile points higher), then you may want to consider taking the GRE instead.
And be sure to check out our GMAT vs. GRE infographic for even more help deciding which test to take!