Which is better: IIT Guwahati mathematics and computing or ECE?

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.