If your main goal is to study economics, maths and statistics then opting for IPM at IIM Indore would be a very good idea. However, the fee structure is very high. INR 4,00,000 per annum for domestic students and for international students, it is INR 6,00,000.
You will also have to study subjects which you will necessarily not like such as sociology, psychology, etc.
Another drawback is that there is no degree for IPM. You will only get a certificate from IGNOU.
In the case of NIT Allahabad, it is a reputed institute for engineering. You will be able to study subjects that meet your interests. The fees are also very less. In the placement drive of 2020, the highest package offered to the students was INR 49 LPA. Some of the top recruiters were IBM, Adobe, Accenture, Tata Steel, Capgemini, etc. The average package was INR 10.28 LPA.