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The admission to National Institutes of Technology (NITs) is based on the JEE Main scores and class 12th marks, and the cutoffs for admission vary every year depending on several factors such as the difficulty level of the exam, the number of candidates who appeared, and the number of seats available.
As per the previous year's cutoffs, it may be difficult to get admission to the NITs with a score of 70 in JEE Mains, especially if you belong to the OBC category. However, the cutoffs change every year, and the cutoffs for this year may be different from the previous years.
In addition to the JEE Main scores, most NITs also have a minimum eligibility criterion for Class 12th marks. As you have scored 79% in Class 12th, you meet the minimum eligibility criterion. However, meeting the minimum eligibility criterion does not guarantee admission to an NIT.
It is recommended to keep an eye on the JEE Main cutoffs for this year and the counseling process to have a better understanding of your chances of getting a seat in an NIT. You can also consider applying for other engineering colleges that accept JEE Main scores, including other centrally funded institutions, state-funded institutions, and private universities.

The answer for your question is unbounded , though I will tell you some key points .
First of all there are very less student who appear for both and get a notable rank . My advice to you is that you choose any one of them (IIT or AIIMS) as they both differs by a bridge of biology subject.
Just get regular to your study with the thinking that there is no shortcut to success . Never keep any doubt in your mind just clear it by asking to the concern teacher . Appear for mock test and try not to do much negative marking .
If you want best decision making for your study days purchase a book wriiten by Arpit Aggarwal AIR 1 in the year 2012 .The name of book is MY ENCOUNTER WITH IIT JEE .
All the best .