Both programs are equally good in their respective fields and so are the institutions offering the programs. It’s important to consider what you expect from the program and what you plan to achieve after graduation to make the right choice.

My sister was in a similar dilemma as yours and eventually, she opted for MCA from IIT Delhi.This program has many courses similar to CS but the only problem is, the pedagogy adopted has a more theoretical approach than practical. Moreover, at some point, you will start questioning the parity of the faculty and will have to resort to self-study.

But here is the bright side, most companies coming for CS placements consider MCA students too, and offer decent roles.

Although I am not well aware of the situation in Roorkee, I can guarantee a true coding lover will prefer CS to MCA any day.

Both IIT BHU CSE and IIT Guwahati MnC are excellent options and the choice of the branch is a personal matter depending on the candidate's preferences rather than the credibility of the branch. Here are a few parameters on which we can draw a general comparison between the two courses.

• Course structure: IIT Guwahati’s MnC program has a well-structured curriculum with the perfect blend of Computer Science, finance, and Mathematics courses. By the end of the program, you will be eligible to sit for software as well as finance placements. IIT BHU CSE too is known for its flexible course structure with a plethora of electives to choose from.
• Coding culture: Undoubtedly, IITBHU has a better coding culture than IIT Guwahati. The ambiance is quite competitive at BHU if that’s what you are after. However, MnC too is gaining popularity and the decreasing opening rank can be seen as a proof of the same. 
• Peer group: High JEE rankers prefer IIT Guwahati over IIT BHU and thus the peer group of IIT Guwahati is more refined and superior in quality. 
• Campus and student life: IIT Guwahati has an amazing campus and its students get to live a very dynamic and lively college life. IIT-BHU’s campus on the other hand is underdeveloped and you can also find student politics here. IIT Guwahati is the best choice for nature lovers who like solace and peace while IIT BHU is for those who want to experience city life as well. 
• Student life: Both institutes have great clubs and activities to promote the holistic development of students. Students are allotted single rooms right from the first year at IIT Guwahati which is different from IIT BHU. Mess food is better at BHU. IIT Guwahati is a clear winner in sports, cultural and technical clubs, etc.
• Placements: Both institutes have equally good placement scenarios with major recruiters like Microsoft, Google, Tower Research, Flipkart, etc. visiting both these campuses. CS and MnC students receive similar placement offers and in fact, being in MnC makes you eligible for both finance as well as software jobs. 

Both the institutes and branches have their own strengths and weaknesses and the final decision should be based on what you want from your degree. If it’s a competitive environment you are after, go for IIT BHU, while if it’s a rich college life experience you want, then IIT Guwahati is your destination.

I am assuming you have no specific interests and are looking for a branch that offers good job opportunities. In that case, Maths and Computing at IIT Guwahati is best. With the unique blend of Mathematical concepts and CS concepts, this program has become one of the most coveted ones only second to CSE. Indeed, MnC has an immense workload and is considered difficult but so is ECE. However, if you are not interested in Maths at all, and are a research enthusiast, Electronics is better than MnC. Electronics will give you an opportunity to explore both IT and hardware industries. However, it’s very difficult to secure internships in CE than MnC and this might demotivate you a bit. 

Concludingly I would like to comment that MnC is a good option in the short run while ECE will prove to be beneficial in the long run.

If you are considering pursuing Mathematics and Computing at either IIT Kharagpur or IIT BHU, it is important to evaluate the strengths and opportunities offered by each institution. Here are some key points to consider in this regard:

• IIT Kharagpur's Mathematics and Computing program is considered to be better than IIT BHU's program by many experts and students in the field.
• The MSc. tag does not cause any difficulty for Mathematics and Computing graduates from IIT Kharagpur.
• The placement records in Mathematics and Computing at IIT Kharagpur are impressive and almost on par with the placements of Computer Science graduates from the institute.
• The opening and closing ranks of the Mathematics and Computing program at IIT Kharagpur have jumped by 2500 ranks in the last 5 years, indicating a growing demand for the program.
• Harshyt Goel, an alumnus of IIT Kharagpur's Mathematics and Computing department, received a package of over 80 lakhs per annum from Facebook (Silicon Valley job).
• Recent Google Summer of Code selections in 2017 from IIT Kharagpur had 8 Computer Science students and 7 Mathematics and Computing students, indicating the strong performance of the latter group.
• IIT Kharagpur is considered a "grand old" IIT with a strong reputation and legacy.
• Mathematics and Computing at IIT Kharagpur are considered to be equivalent to Computer Science and are even considered to be better for open-source developers, according to some experts.

If you are interested in pursuing Mathematics and Computing, IIT Kharagpur is a great choice with a strong reputation, impressive placement records, and opportunities for high-paying jobs both in India and abroad.

Whether IIT Patna CSE is better or MnC at IIT Guwahati, depends on what you want to do after your graduation. 

If you have an interest in pure and abstract Math and want to do research in Maths, theoretical computer science, Set theory, Group Theory, and Complexity Theory, then the IIT Guwahati MnC program is the best for you.

However, if you have an interest in coding and want to become a competitive programmer, or a software developer, and research in areas other than Theoretical Computer Science, then IIT Patna CSE is the right choice for you. Extensive research on every CS field is done here.

Basically, the academic workload of the MnC program at IIT Guwahati is too much with a very rigid curriculum that will spare you no time to focus on coding. No doubt, the MnC program too has excellent job opportunities in finance, banking, and software jobs. But, the demand for CS students is much more than MnC students and is expected to be increasingly so over the next few years. 

Common courses of CS and MNC include theoretical computer science, some being computer networks, and operating systems while the rest of the courses are related to abstract Maths/pure Math and are highly rigorous in nature. Contrary to popular belief, there aren't many common concepts between MnC and CS. 

IIT Guwahati will give you a slightly better campus life in comparison to IIT Patna considering its scenic campus and high-level fests organized by the institute.