Which branch of nit Patna is the best?

The very first thing, you should have mentioned your preference for comparison. Best in which way? placement? teaching?or else?

let me cover all these.

computer science department

• placement is best w.r.t other branches, with companies like Snapdeal, Oxigen provide an annual package of 15.6 lakhs. At least 60% get placed every year.
• there are approx 93 seats in CSE which is further divided into 3 groups for laboratory purpose. (guiding all 93 at a time is hectic for lab attendant)
• one authorized international club IEEE is active in here.