Which is better at CUSAT, IT or EC?

Both the options are good. There is no such difference in the quality of education, either in these two branches, or any other branch in CUSAT.

They make you work hard, focus on every detail, and stress a lot on the practical classes and labs.

As for the faculty, 85% are permanent. As for the quality of faculty, everyone will have a different view. According to my friends at CUSAT, the only difference you will find between the branches is that the EC people toil 3 times harder than the other branches.

According to the overall placement statistics the average and highest CTC offered to the students is 4 LPA and 15 LPA.

You should choose the branch that is better for you. Think about the branch where your interest lies, will you be able to manage the workload efficiently, does the subject interest you, or which branch has the better placements matter. However, I would like to advise you not to be bothered by placements any more.