Diploma

Diploma in a layman language is a short term course generally up to 2 years which mainly focus on training a person in a particular field. They are one of the quick and best way to get a job as their course is more practical oriented. The importance of Diploma as compared to degree is relatively less. DEGREE on the other hand, is a long term course which varies between 34 years for Bachelors, 2 years beyond Bachelor for master degree, depending on the course. Degree provides more in depth knowledge about a particular course then Diploma. Earning a degree opens more doors for opportunities as compared to Diploma. In fact, various career options require at least a Bachelors degree.

Hello Aditya,
You can reappear for 12th if you have confidence that you can score more than present. Or you can go for 3 year Diploma on the basis of 10th Standard Percentage. The Choice is yours. Its not about value it's about if you really wanna do that or not. If you really wanna do Engineering and have passion and interest in that you can go for Engineering or can change you career stream. You can either choose Diploma then Degree or you can reappear for 12th. Also please analyse why you scored so low. Ask yourself if you really have interest in Science Stream or you selected it beacuse of peer pressure and family pressure. See this analysis is important for your betterment. Please don't go for a branch you don't have interest in. Reappearing for 12th is good option. Do well and Score good. Also give JEE Mains again and try to Score good in that.
Good Luck!