I want to do Masters in construction management. Should I opt for MBA or M.Tech?

I would suggest you to go for MBA in construction management for its wider career opportunities. Check courses of RICS School of Built Environment college to understand better about career scope from the link mentioned https://www.shiksha.com/college/rics-school-of-built-enviornment-noida-36312/cour

It would be better to go for MBA in construction management if you have interest in business side of construction and civil than MBA is better option. Some of the activities you need to do as construction Manager – Prepare cost estimates, budgets, and work timetables Interpret and explain contracts