Hello Samrat, 

B.pharma+M.pharma is hands down the better choice in terms of educational qualification and job opportunities. Such as working in MNCs, research centres, teaching positions etc

Diploma in pharmacy is a 2 year course which can be done after completing 10+2 and is ideal if you wish to work in a medical store, small business etc. A diploma in pharmacy can earn you a lateral entry into B.Pharma as well

To conclude B.Pharma+ M.Pharma is far superior to D.Pharma albeit much longer in terms of duration of course

It would be worth mentioning here that there is another degree called Pharm.D which is a doctorate level degree in Pharma and must not be confused with D.Pharma which is a Diploma 

I hope this resolves your doubts, good luck! :)