Firstly, you should know that IIIT UNA is a new college and although it has the IIIT tag, it hasn't been ranked by any esteemed Ranking platforms like NIRF. Its classes are also facilitated by NIT Hamirpur's faculty and the campus and faculty are nice. 

As far as NSIT is concerned, it ranks #76 on the NIRF ranking portal for engineering and has a better location in Delhi than Hamirpur, because of the facilities and professional opportunities available. 

Here are some more pointers to help you understand better -

• If your interest lies in the program rather than the institute, then go for CSE. Although first reflect on the placement scenario of IIIT UNA, whether they receive good companies or not; if the package is satisfactory, and if speedy placements are facilitated after the course is over.
• When you take a look at NSIT, then you should know that you'd be able to build a good career as a software engineer with the ICE program, but the management will be a little difficult because of the delicate balance between coursework and developing your programming skills.
• Most ICE alumni are now pursuing MBA or working other non-technical jobs. For non-tech, NSIT offers better opportunities.

Here's a table on the placement scenario-

Lastly, decide according to your future goals and whether you'd like to pursue CSE or instrumentation.

NSIT Delhi is a leading institute in India and ranks 76 among the engineering colleges as per NIRF 2020 ranking. This institute is an excellent place for quality students and offers nearly 100% placements every year.

IIITM Gwalior is a fully IT-oriented institute and ranks 100 among India’s top engineering colleges as per NIRF 2020 ranking. This institute provides 90% placement to its students in top-notch MNCs. 

Admission Process 

NSIT Delhi:

• The essential eligibility criteria are a minimum of 75% marks in 10+2 with PCM as compulsory subjects.
• The final selection of the candidates depends on the JEE Main scores.

IIITM Gwalior:

• The primary eligibility criteria is a minimum of 75% marks in 10+2 with PCM as compulsory subjects.
• The final selection of the candidates depends on the JEE Main scores.

The following table gives a brief overview of both institutions:

Placements:

The placement scenario at IIITM Gwalior is one of the best than other IIIT's. 

Mostly all the top companies, including technical and non-technical visits, every year for the placement process at NSIT Delhi.

The top recruiters are Google, Cisco, Amazon, Microsoft, Dell, IBM, Verizon, Accenture, Wipro, Flipkart, Adobe, etc. 

Both these colleges provide quality education with successful placements. The students pursuing a course in any of these colleges will be an excellent choice.