Sir i think diversification is a better option as we can see from past that some of the nifty 50 companies shows bad performance. Best example is Tata Motors, After acquiring JLR its performance is steeply declining, with change in time and demand companies needs to upgrade their business model otherwise they can be like Nokia. And retail investors like us will never know that how transparent and clean are the accounts of a company like YES Bank. So it is better to diversify the portfolio.