Dear Sushil ji,
According to me both DLL and LLB are equally better / important. First one is a diploma whereas the second one is a bachelor degree.
DLL is a diploma in Labour Laws. You study all labour laws in this course. In LLB, you study labour laws along with criminal law, civil law, family law, contract law, property transfer law, taxation law, administrative law, company law, environmental law, Law of evidence, Indian constitution and many more. Only four labour laws you study in LLB.
To do specialization in labour laws, you need to do DLL but you should not ignore LLB. I mean to say, you need to do both but, HR compliance point of view, DLL is must.
Ultimately, what is important, is the KNOWLEDGE you have. The certificates / degrees are the entry pass to get in to employment. Your certificates / degrees should be seen on your face.
This week itself I came across one HR professional with many qualifications telling me PF is not applicable to labour class.