Prefer IT at IIIT Allahabad than CSE at MNNIT if you only consider placements as a factor. Average placement packages in IT@IIIT are a tad bit on the higher side than CSE@MNNIT. This can be attributed to the lesser strength of around 80-100 eligible candidates and almost same packages provided by the companies visiting both the campuses. Hence lesser variation in range of packages compared to MNNIT with around 150 eligible candidates, leading to a higher variation in package range.
P.S. : Your branch or college doesn’t really matter when it comes to placements. If you are deserving and have command over your strengths and know how to code, you can easily bag a good package, irrespective of the college.Also almost all the companies visit both the campuses, barring few exceptions.