See ratio of no of companies visiting campus to no of students is more in IIIT. In simpler words more opportunity in IIIT. You'll enjoy coding environment. You can check spoj and other coding sites. IIIT is at better position than MNNIT. Even fests are better than that of MNNIT.
But at MNNIT you'll enjoy all the name and fame of college. Fees is also less and you'll get good job opportunity.
You can opt for any. But I'll strongly suggest to go for MNNIT. You won't regret your decision.

Both are good in which you want?

I Thik IT branch in mnnit is better

MNNIT Allahabad

Admissions Courses & Fees Cutoff Placements Reviews

Shortlist

Brochure

IIIT Allahabad

Admissions Courses & Fees Cutoff Placements Reviews

Shortlist

Brochure