The answer of that question depends on a lot of factors: i. If you prefer paper-based exams, go for IELTS, as it provides that option. (it should be done if your typing speed isn't that great, so you can write the short-answers on paper instead.) ii. If your Vocab isn't that great, go for IELTS as it has comparatively easier vocab. iii. If your want to avoid complex Maths, go for TOEFL as it has easier Maths as compared to IELTS. iv. The speaking Interview in TOEFL is computer-based and can be given along with the test, but the interview in IELTS is taken by an actual human being, so you can choose the exams on basis of your comfort level. v. When it comes to the interview/speaking part, since TOEFL's speaking evaluation is done by the computer system, it will scrutinize your accent as well as your fluency, but in IELTS, the conductor will focus mainly on your fluency and personality (body language.)