Both IIT Guwahati for Biotech and MNNIT Allahabad for IT are extremely different courses in terms of the scope they offer.
Go for Biotechnology only if you are genuinely interested in it because core placements are miserable and there is a dearth of job opportunities. Most students get placed in Analytics and other non-core sectors and only a few manage to secure a core job. So go for this only if you want to pursue higher studies.
MNNIT Allahabad’s IT program offers excellent job opportunities but lacks in terms of research and exposure. The coding culture is very good here but the academics is poor. The placement scenario is great second only to CS placements. If you aren’t sure enough consider the following points before making the final choice
Concludingly, if you have a specific preference for research and higher education, go for IIT Guwahati else MNNIT Allahabad is the best option for you.