Both are the decent colleges, It also depends on interest which branch you want to go. But as per the analyzing report of Careers360 Cochin University of Science and Technology, Kochi has AAAA rating which means very good. The rating is based on the research of the college on various parameter like faculty, Placement, Infrastructure etc. You can also check teh genuine reviews of the colleges with the given below links.

https://engineering.careers360.com/colleges/cochin-university-of-science-and-technology-kochi

https://engineering.careers360.com/colleges/government-model-engineering-college-thrikkakara

Good Luck!