2. Mechanical Engineer will have fixed hours of work but for Doctors it is most probably not.
3. Most probably Doctors will make more money than Mechanical Engineers (generally) (Also it can be many folds)
So if your ambitious about money then Doctor is the way to go between the two.
4. Doctor is more responsible job that Mechanical Engineer in my opinion.
5. Social status for Doctor is higher than that for Mechanical Engineer.
6. Social life for doctor is somewhat hampered due to commitments.
This is my personal opinion.
Atla Akshay Varma
This aside both mechanical and medicine have very good opportunities. This will also be based on lot of aspects like, if you are in Germany, engineering is considered the best choice, due to the vast industries that the country comprises of. Similarly even if you are having lesser opportunities for the course you studied, there is always the chance to go abroad right. Don't worry you will find a path, for any sort of obstacles, so all the best.