which is hard aiims or neet

If you have a good foundation of concepts and do not believe in the myth of cramming, then no, it isn’t tough.
Majority of people out there cram everything up, and AIIMS or NEET paper is designed in such a way that you will be given extra information, just to confuse you in the questions without having any relevance to the question. If you have a good and clear grip over the concepts, then you’ll be able to solve them efficiently.