I think OP is talking about Within the Binance Exchange. if you use BNB as trading fee, you'll be able to trade for a lot cheaper than Eth or BTC Fee. and by faster he probably mean Transactions But in Binance chain. if you use ERC20 BNB it is not faster at all. it is same as ETh. but in Binance Chain (their own blockchain, they launched recently) BNB coin seems very fast.
BNB is very useful for the traders, as Binance provides a 25% discount on the trading fee if you make the payment with BNB. Especially for day-traders, 25% can make a lot of difference. And any token within the ERC-20 platform will attract high gas fee and result in delays, but that is not the case when you use BNB within the Binance chain. But you should be cautious while using the Binance chain, as it is relatively new.