IIITDM Kancheepuram is an institute of national importance and it has an advantage over the other two institutes as both the institutes are IIITGs in PPP Mode. The bill to declare PPP mode as institutes of national importance is still pending in parliament. 

Here are a few pieces of information about the CSE/IT in the campuses mentioned in the question. 

IIIT Guwahati:

The institute started in the year 2013 and has a strong CS department with a good number of experienced faculties. 

• Prof Gautam Barua who is the director of the CS department at IIIT Guwahati was also the director of IIT Guwahati from 2003-13. With his immense experience, he aims to build the department strong. 
• Coming on to the curriculum of CSE/IT, it is well designed to suit the growing need of the industry. The intent here is to complete all the core subjects in the first 6 semesters so that students can choose the type of industry they want to get into. Like in the 4th semester, there is a subject called Computer Network which is generally a subject of 5/6th semester in other institutes. 
• In the CS department, IIIT Guwahati has come up with the Ph.D. program as well. 
• There are many advantages to join IIIT Guwahati but only a single disadvantage is there i.e. Location. But if you love to travel and nature, Guwahati is a place for you. 

IIIT Sri City: 

• The number of faculties at IIIT Sri City is nearly half as compared to IIIT Guwahati. 
• They also have MS and Ph.D. programs which indicates that they are also very active with regard to research. 
• They are being mentored by Prof. UB Desai who is also the director of IIT Hyderabad and a pioneer in System and Network Research in India. 

Both the colleges have their advantages and disadvantages. You have to analyze which is better for you to pursue B.Tech in CSE/IT as per your parameters. Good luck.

No, IIIT Sri City is not an inferior institute. It is decent to invest your time and money in it. Below mentioned are a few features of the institute.

• The infrastructure has developed quickly in the past years to make it a fully-functional campus.
• The worthy students are filtered through JEE Mains and admitted to the institute. Many students have achieved top-ranks in the contests held around the country. Even a few seniors have secured admissions in the best universities of the world like MIT (USA), Carnegie Mellon University, etc.
• The system of IIIT is worthy. You do not have to prepare records, journals, and other things to submit. The traditional methods have been abolished. The assignments are connected to the practical learning experience. There is no waste of time and resources.
• The schedule is not tight. You will be able to manage all the crucial things like academics, extra self-learning things, and recreational activities at weekends.
• The students have joined the industries like E-Commerce, Ed-Tech, Data Analytics, IT Product and IT Services, Manufacturing, Consulting, Augmented, and Virtual Reality.
• The companies like Amazon, Hyundai, Finsol, etc., visit the campus.

It is a good institute, so try to make the most out of your experience there. It is important to make the right choices in terms of peers, college groups, clubs, etc.

Among the above two institutes, IIIT Pune is the definite choice, considering a number of factors including IT industry exposure, internal competition, and overall development in the institutes. I know a few people from both institutes, so I can give you an idea about them.

Location:(Winning Institution - IIIT Pune)

• Presently, Pune is considered to be a large IT hub, with offices of several companies from different sectors too. In 2018, Pune was listed as the second most paying city for software engineering jobs in India, after Bangalore. 
• For research-minded students, there are several institutes in Pune including the National Chemical Laboratory, and the Indian Institute of Science, Education, and Research (IISER, Pune). This will give you a bundle of opportunities.
• Pune is a metropolitan city in itself, whereas Sri City is 74 km away from the closest metropolitan city, Chennai.

Student Intake:

IIIT Pune takes in a total of 120 students per year, 60 in CSE, and 60 in ECE. On the other hand, IIIT Sri City takes in 270 students per year, 200 students in CSE, and 70 in ECE. Therefore, it is evident that a lesser number of students will get better attention from professors, less internal competition, more opportunities, and a focused learning experience.

Mentor Institute:

IIIT Pune’s mentor institute (College of Engineering, Pune) is located in Pune itself, whereas IIIT Sri City’s mentor institute is IIIT Hyderabad, 608 km away from it. So it is easier for IIIT Pune students to attend mentor institute events, lectures, and facilities.

Extra-curricular:

Students from IIIT Pune have excelled in several sports events too, like IIT BHU’s Spardha. There are several Coding, Robotics, and technical events in which IIIT Pune students excel.

Future Development:

• The growth pace of IIIT Pune is very fast. With a number of hardworking students and dedicated professors, IIIT Pune will soon reach a good height and will be considered a leading institute.
• The 100-acre campus construction of IIIT Pune will get completed, which is being set up in between the city’s core industrial zone. After IIIT Pune receives its own director, the growth rate is bound to increase and so is the development of the institute.

Considering all of the above factors, IIIT Pune is a definitely better choice, providing several opportunities to students in the industry and research fields.

Among the above two institutes, IIIT Sri City is the better option, considering several factors like placement and overall development of students in the institute. The table below gives a brief level of comparison among the two institutes.

Key highlights:

• If you are interested in coding and computer science-related subjects, IIIT Sri City is definitely a better option.
• Although IIIT Sri City is also a new institute, the rate of growth of the institute is quite high in terms of infrastructure, placement, etc.
• The mentor cum director of IIIT Sri City is Prof. U.B. Desai, who is also the director of IIT Hyderabad. He is a man with a lot of knowledge and works best towards the advancement of the institute.
• Comparing these IIITs with VIT, they are better than VIT in many aspects other than the campus. Within the next 2-3 years, these IIITs will surely surpass VIT in every aspect.

Therefore, you should prefer IIIT Sri City as their first option, following with IIIT Guwahati for a B.Tech degree in CSE.