The short answer is that you should take the test you will score better on. You can take a free GRE practice test and a free GMAT practice test online to see which test gives you a higher score. The long answer, unsurprisingly, is a little more complicated. Many business schools say that the GMAT is a better predictor of your performance during your first semester of business school than the GRE, and prefer that applicants take the GMAT for this reason. Some recruiters for management consulting firms and investment banks also use GMAT scores to find future employees, so taking the GMAT could be more useful in the long term for your job search. On the other hand, if you are unsure about whether you want to go to business school or graduate school, you may want to take the GRE instead. Likewise, if you have already have a valid GRE score, you may want to focus your energies on perfecting the other parts of your application instead of preparing for another standardized test. If you are applying for a dual MBA program, you may also want to use your GRE scores to save yourself the trouble of taking two tests. Finally, if price is a consideration, the GRE is about $100 cheaper than the GMAT. All that said, if you have not taken either test but know for sure you are applying to business school, you should take the GMAT.