If we have prepared properly for JEE then the only difference in them is the level of question and pattern and pressure:1)LEVEL OF QUESTIONJee mains papers contain direct questions from NCERT and the number of questions in Mains requires less thinking approach for an average score of 200+ but for 300+ it requires logic and some guesses and more confidence in oneself(be careful it's not overconfidence only more confidence)Whereas JEE ADVANCED has much more logic required, much depth in a subject required for scoring and getting into IIT’s as such this can be felt properly on your side depending on your level and it studies of u go through the previous JEE papers2) PATTERNThe most complicated thing for any student and may be for the faculties also as such it creates a frightening situation in the JEE ADVANCED exam..whereas mains has the same pattern every year and also most of the coaching institutes conduct more Mains test rather than ADVANCED so Mains pattern is felt easier..and frankly speaking Mains pattern was felt difficult in 2016 rather than ADVANCED due to the partial marking..yea the paper level also matters but if level would have been same then ADVANCED was difficult rather than MainsAlso, most of the students practice single objective to their Max rather than Multiple, integer, comprehension, Match the following and all3)PRESSUREYea the most important thing if a student is prepared completelyThe reason why this is important is if a student is well prepared then obviously he needs to aim for IIT rather than NIT as one doesn't aim for NIT the pressure is reduced automatically by around 30–40% in the exam.Most of them aim for IIT and not NIT so even removing the preparation point the pressure reduces