Hello,

The quality of the course depends on the institute, faculty and the student who is pursuing.JEE Main is an entrance exam for admission in UG courses like B.tech/B.arch/B.Planning whereas polytechnic is a diploma level engineering course after that you need to complete your B.tech.To be eligible for JEE Main a candidate must have passed 10+2 or its equivalent from a recognized board or university.Whereas the eligibility for admission in polytechnic is that a candidate must have passed class 10 with Mathematics and Science subjects.

If you qualify in JEE main and secure a decent rank you will get seat in an NIT or GFTI.These are reputed institutes in India which offers first class education.If you study diploma then you will have techinical knowledge.Ofcourse your first must be IITs/NITs/GFTIs But it depends on your aptitude and hardwork.