1. Indian stock market collapsed after Harshad Mehta scam surfaced. Traders/investors didn’t trust stock market and it was BSE who lost its credibility. NSE was a new entrant, a fresh one. No judgments were attached to NSE, thus it was the only choice for investors
2. While BSE worked as a black-box, NSE brought transparency and rebuilt the trust of investors in the stock market.
3. NSE eliminated the monopoly of brokers in the stock market and allowed every eligible trader/investor to buy-sell directly.
4. NSE depository NSDL removed all the problems attached to a physical certificate. No more physical papers, no more worries.
5. Stock market runs on retail traders, who place trades of small turnover. Thus low charges of NSE for lower turnover trades are obviously better.
6. NSE stocks provide more liquidity than BSE, thus a better choice for investors.