IPU is a Central government university run by the Government of India, on the other hand, Amity and UPES are Private profit-making universities and are just hungry for your money.
Only the admission criteria shows what is the difference between IPU and these two. You need to qualify JEE mains in order to get admission in IPU. UPES conducts their own exam but anyone who writes the exam can get any branch they want without any hesitation and AMITY just call you to come to the university and just pay the fees.