Hey  Biju

Both IIT patna and IIT dhanbad are great choice. In IIT dhanbad,The placement percentage is quite high as in most of the IITs. Around 80% of the students in B.Tech programmes get placed. Placement percentage of the branches like mining engineering and computer science is 90% whereas the civil department lacks a bit regarding placements. The highest salary package offered was 36 LPA and was offered to the students of CSE department. 

Infrastructure : The infrastructure of the college is quite good and is still developing. 

On Other hand, IIT patna

Placements in the college are good with an average salary package of 18 LPA being offered. The highest salary package offered this year was 40 LPA, and the lowest salary package offered was 5 LPA. Google, Microsoft, DE Shaw, Amazon, and other companies with good working environment visit the college for conducting placement drives. Over 90% of the students in both B.Tech and M.Tech courses are placed.

Infrastructure : Labs and classrooms in the college are well-equipped. But there is no auditorium in the campus. Most of the construction is still going on. Hostel rooms are really cramped up.

you Will Enjoy College life at both the colleges

I Hope It Helps 

Good Luck