The first thing you should consider is whether you want to pursue a Ph.D. or want a job after the completion of the course. I have a few friends at IIT ISM and I can tell you there are very few good faculties for CSE if you want guidance regarding Ph.D.

For any information regarding the faculty and research projects of IIIT Allahabad, you can visit both their faculty profile page and set a legitimate comparison with IIT (ISM).

Here are some other parameters of IIT (ISM), which you may find useful.

Placements:

The job prospects are increasing every year and the change is noticeable since its conversion to IIT. The institute also had a new director from IIT Kanpur. There also was a significant change in the placement cell, and the M.Tech placement stats have been kept under consideration, alongside B.Tech only after that.

The latest stats are as follows,

Moreover, the summer and 6-month internships have also been good over the past few years. For instance, the 2021 passing out batch has received several summer intern offers from companies like Goldman Sachs, Amazon, and Microsoft.

If you prepare for the coding session interviews from the beginning of the 1st year, then you are more likely to obtain internship opportunities. You can convert it to PPO before the placement season begins.

Other Parameters:

There is another thing you should consider. It is the number of students from either CSE or IT in B.Tech + M.Tech taking part in the placement season,

A total of 372 students participated in the placement drive from IIIT Allahabad while 203 participated from ISM Dhanbad.

However, there might not be a significant difference between companies that visit both institutes. Fewer participants in placements mean less competition.

So, I will suggest that you take all these factors into consideration and also do your own research. Consider other options too, if you have any.