Let me just point out a few differences
1. MS is more of a research program, M TECH is like another degree or double certification.
2. M TECH is through GATE, MS is through GRE and various other exams + interview.
3. Fees for MS is more than M TECH.
4. Course Duration is 2 yrs for M TECH, whereas MS can be more than 3 years.
5. Work experience is a bonus for MS but to M TECH after working is not preferred.
6. Unless you have done any research or project and publish papers wrt any domain, MS degree is similar to just a show whereas M TECH would fetch you a job no matter you have done a good project or publish papers as long as you crack your interview.
Hope you take a wise decision.