What is the difference between the GMAT and the GRE?
Essentially, the GMAT predicts how suitable a candidate is for a management related program, whereas the GRE does the same for the following eight graduate school programs: Biochemistry, Cell and Molecular Biology / Biology / Chemistry / Computer / Science / Literature / English / Mathematics / Physics / Psychology.

Both tests have been created for native English speakers, which means foreigners are at an immediate disadvantage, especially in the verbal sections. This is particularly true of the GRE.  The GMAT measures verbal, mathematical and analytical skills that the candidate has developed in education and at work.

The GMAT has for some time been the established test for getting into business schools. It measures verbal, mathematical and analytical skills that the candidate has developed in education and at work. It does not measure specific knowledge of business, job skills, or subjective qualities such as motivation, creativity, and interpersonal skills. Even if a test taker's first language is not English, he or she may still perform well on the exam.

The GRE measures the extent to which undergraduate education has developed a students verbal and quantitative skills in abstract thinking.

The GRE measures the extent to which undergraduate education has developed a students verbal and quantitative skills in abstract thinking. For non-native speakers, the GRE requires a far broader knowledge of vocabulary, writing skills and general subjects than the GMAT. Without good English and writing skills it is impossible to get a good score in the GRE. So, for non-fluent English speakers, our advice in this case is to stick with the GMAT.

Diversity - more than just a GMAT score
Conversely, non-native English speakers hold trump cards other than high GMAT scores. Business and graduate schools are striving to diversify so applicants from countries that have recently joined the European Union, like Bulgaria and Romania, stand a good chance of being accepted, as do those from smaller Ukraine and Kazakhstan. If graduate schools are really interested in an applicant, and the whole application stands out as being special, the school might accept a lower GMAT score. Should these candidates be women, their chances increase three-fold.

Schools are also seeking to broaden their appeal to candidates from wider backgrounds. Candidates are still more commonly from management, finance or accounting backgrounds, but those who can be described as publishers, filmmakers, lawyers, theatre agents or graduates in law, medicine or literature are on the top of the list for business school admissions.  

GMAT or GRE: Essential Differences
The GRE requires you to do the arguing, whereas in the GMAT you analyze what has been argued. The style expected from GRE test readers is more abstract and draws from various sources and disciplines for examples or references, whereas it is more concrete and analytical for the GMAT.  Does a future manager actually have to be able to write his argument or does he just have to be able to recognize a good one?
This supports the suitability of the GRE for the more academically-minded student. Perhaps Stanford and MIT should be congratulated for their foresight in recognizing that future leaders may lie in waiting in academic circles.

What you should do?
The essential advice is to first ask the schools you are applying to which tests they will accept. Look closely at the GMAT and GRE tests and see how you feel about both of them. If you have taken the GRE and got a good score you can always ask the schools if they will consider it. 

Remember, admissions look at the overall package  your test scores, essays, your background and your motivation. Applying for business school is not an overnight decision; it is a new start in your career, whether or not you are accepted.

Websites and personal meetings with admissions directors at the QS World Grad School Tour are most helpful at this stage. If you decide to go ahead with your application, you know you have made the right decision and not just followed a spur of the moment whim. Good luck with your application, whichever test you decide to take.

courtesy:  Judy Martinez and Ross Geraghty (Topuniversities.com)