According to my friends at IIIT Guwahati, CSE at IIIT Guwahati is definitely a better choice. Let me provide some points which will give you a better insight into the colleges.

• The campus of NIT Puducherry is almost 130 km away from the city, located in a remote place known as Karaikal. This hampers placements.
• In NIT Puducherry, 90-95% of students are from South India. So, students from other parts of the country face a serious linguistic problem.
• For most North Indian Students, it is somewhat hard to sustain in the South Indian culture.
• IIIT Guwahati has experienced rapid growth over the last few years, which makes it a much better choice than NIT Patna/ Puducherry.
• There is no home state quota in IIIT Guwahati, so there is no such problem of linguistics as in NITs.
• In addition, there are 18 students in IIIT Guwahati who are from abroad, selected through the DASA UG scheme of 18 seats.
• From 2019, the B.Tech seats were increased by 33% for Girl Supernumerary Quota, because the previous batch had only 3.5% girls. The total number of seats from then is 233.

Therefore, IIIT Guwahati has a lot of advantages over NIT Patna/ Puducherry, which makes it a better choice for students in engineering.