If you are going to take admission for M.Tech in any of these colleges it will be worth the choice. All are quite established and are doing great in curriculum and placements.

But there is always the best among the rest and hence, I would like to suggest you opt for NIT Durgapur. It beats both IIIT Allahabad and IIITM Gwalior. Also, regarding the two IIITs, IIIT Allahabad certainly does better than IIITM Gwalior in competitive programming and placements

• On the other hand, NIT Durgapur holds strong ties with IIT Kharagpur.
• The professors and students both are collaborating on various projects from both institutes.
• The alumni base of NIT Durgapur is also strong. It includes IIT Kharagpur graduates who have completed or are currently pursuing higher degrees at IIT.
• There is a better opportunity in NIT Durgapur as compared to others, in case you are prepared to utilize these.
• If you will seek placement after M.Tech, go for Allahabad.
• In case you are interested in research, I will recommend you to look at the faculty profiles in the respective departments, and make an informed choice.

It is suggested you go for NIT Durgapur. Definitely, do your side of research as well for a clear choice among all the three colleges.