I took IELTS exam. I can make a few comparison for you. The most positive point I found in IELTS is that it is much easier in studying and taking but getting a good score is considerably harder than toefl. Some prefer IELTS because it is handwriten but some prefer TOEFL since in writing part they can benefit from copy paste actions. Scores in IELTS grows by 0.5, however, in TOEFL you've got higher chance of promoting. Further, Most of Canadian and American Univesities require higher score for IELTS in comparison with TOEFL. It should be also noted that most of Iranian examiners are not fair enough in speaking and writing part of IELTS exams. You see, it's completely up to you. You need to prioritize your own criteria. Wish you the best of Luck in your future exams.

TOEFL

you can refer to this link, you can see a comprehensive comparison between them : http://www.applyabroad.org/forum/showthread.php?21207-%D8%A7%D9%86%D8%AA%D9%82%D8%A7%D9%84-%D8%A7%D8%B2-IELTS-%D8%A8%D9%87-TOEFL-%D9%88-%D8%A8%D8%B1-%D8%B9%DA%A9%D8%B3

Thank You Rainy :)

I never took any of mentioned exams but I think this will really help you: http://www.i-studentadvisor.com/blog/education/international-students/ielts-vs-toefl-which-is-better/