Hello MEET, 

It is important to think about which course of engineering you want to pursue before making a choice. For example if you want to pursue electrical then diploma would be a good choice as you will have more hands on experience. Diploma in any engineering subject will give you more practical experience but your chemistry, physics and maths will be less developed as compared to 11 and 12 pass out students. 

If you aspire to join any IIT or NIT then I would suggest you go for higher secondary exam as the CBSE 11 and 12 pattern is very similar to the JEE entrance exam papers. And there is more time to prepare for entrance exams with higher secondary course than with a diploma (feedback of actual students). 

Hope this helps  :) 

Hii ,

If you are serious about the Engineering and want to pursue your Career in the field Of Engineering then go for Diploma without any doubt.You will have more practical Knowledge.Most of the subjects in Engineering are already covered in Diploma.Moreover Diploma students have more practical Knowledge.So Diploma is better one.

Thank you.