Which are best courses after diploma in mechanical engineering?

There are so many opportunities for higher studies after diploma in mech.

You can join various mechanical oriented B.tech courses like....

B.Tech Mechanical

B.Tech Automobile engineering

B.Tech Mechatronics

B.Tech Plastic engineering

B.Tech Aeronautical engineering

B.Tech Marine engineering

AME Aircraft Maintainence Engineering

If you want to do any short term courses there are so many options..

These are all 1 year courses listed below:

CNC training

CAD Training(autocad,proe,catian)....

Some colleges offer B.tech lateral entry 2nd year for diploma students.My opinion is better to continue ur studies from 2nd year....