dear student

NISER is one and is under DAE while IISER's were 7 and are under MHRD.

The course structure is different. At NISER, you study physics, chemistry, biology and math for one year while you do that for two years in IISERs.

Fee is higher in IISER while it is lower in NISER.

IISERs are institutes of national importance but sadly NISER is not yet.

NISER has good faculties in all the departments, is one of the best in physics and experimental chemistry. IISER Kolkata is good for physics, IISER Pune is good for chemistry and IISER Mohali has a lot of people doing algebra in maths. The departments are one of the best in the country.

hope it helps

All the best!!!