NIT Surat Mechanical Engineering is a better option among these. The institute has an excellent mechanical faculty. NIT Surat placements are also good for Mechanical. Each year around 80% of students get placed from the branch. The average CTC received by the students of Mechanical is around INR 6.09 LPA. While the highest CTC for the branch is around INR 19 LPA.
It is very important to get clear about the dual degree and whether it is available in both the institutes with the same branches or not.
SVNIT's mechanical branch is very good as the faculties are well experienced and they won't let you down in any circumstances and would be very supportive. They are quite good and would help in academics and non-academics things also.
From the placement perspective, the placement record of SVNIT mechanical engineering is quite high. Many core companies for the core branches like mechanical visit the campus for the on-campus placements. They also offer two student chapters to enhance and improve the student's technical skills.
IIT's are considered higher than the NIT's and are provided by more budget. Therefore, they have slightly more advantages than NIT.