In previous posts, I wrote you could take the GRE instead of the GMAT, and the IELTS instead of the TOEFL.
Well, I did actually take all those tests: GMAT, GRE, TOEFL, IELTS. But I spent much more time with the GMAT than with the GRE, and also with the TOEFL instead of the IELTS. So, I don't feel prepared to write much about the GRE and the IELTS. But there are a few things I would like to point out.
I regret not paying enough attention to the GRE. For business schools, the GMAT is more traditional and more widely accepted, so it seemed logical to me to focus on the GMAT. But the number of business schools accepting the GRE for their PhD programs is really big nowadays. Your preparation for the GMAT will be useful for the GRE too, with few adjustments. They are different, but they test almost the same things.
I recommend you take both the GMAT and the GRE, and then see which one is your best score to include in your application. You can send them both, if you wish.
But the main reason I recommend taking the GRE is the percentiles in score. Just like the GMAT, you get not only the score, but a percentile which shows the percentage of test takers who score below you. And the percentile for the Quantitative section of the GMAT has changed too much in the last years. Now, the only way to get a Quant score above 90% in the GMAT is if you get a perfect score of 51. However, according to the 2016-17 GRE Guide, you can be above 90% anything between 166 and 170 in the GRE Quant section. And it just happens that the Quant section of the GRE is considered easier by many people than the corresponding section of the GMAT. So, with less mathematical skill you can get a higher Quant percentile at the GRE. So, it's easier to make your application look stronger in the quant section using the GRE than usingh the GMAT.
Why can you get a higher percentile with less skill with the GRE? I think the answer lies in the difference between the people who take the GRE and the people who take the GMAT. The GMAT is only for business schools. And business schools (MBA mostly) draw a lo of applicants who are extremely strong in Mathematics. Engineers and economists, for example. From countries like China, South Korea, and India, for example. So, it's really hard to get a Quant score better than those people. The GRE, however, is used for graduate programs in general, not only business. People who apply to a PhD in Literature or Arts, for example, take the GRE too. And those applicants are usually not so strong in the Quant section. So, it is easier to get a Quant score better than them.
Ok, that's only valid for the Quantitative Section. Not necessarily the Verbal section. But, I think the Verbal sections of both the GMAT and the GRE are hard for people in general, although the GRE demands a better vocabulary. And, for many business PhD programs, they are more worried about your Quant skill than your Verbal skill.
So, that's what I wanted to write about the GRE.
Now, the IELTS. If you are an international applicant, you should focus on the TOEFL if your interest is doing a PhD in the US. The reason is that it seems all schools accept the TOEFL, but many do not accept the IELTS (which is stronger in Europe). But, if your TOEFL score is not that great, the IELTS may be an alternative for some schools.
As I wrote before, my scores for the listening, reading, and writing sections of the TOEFL were very good. But my score for the speaking section was lower, only 23. And there were schools which demanded at least a score of 25 in each section, So, my total score of 110 was great, but my speaking score was not enough. In those cases, I was able to sent my IELTS score instead of my TOEFL. Because I like the speaking section of the IELTS a lot more than the TOEFL's. In the TOEFL, you talk to a computer recorder using a mike. In the IELTS, you have a real conversation with a real person in front of you. I think it's much better to show if I can talk in English or not.