What is STP?

This suggests that there shouldn’t be any conflict of interest between brokers and traders, as STP brokers make money by adding a small commission, or markup to the spread. Whether a trader wins or loses, the broker gets the same markup, whereas dealing desk brokers make money out of their clients’ losing trades. STP brokers, on the contrary, benefit more from winning traders who trade more and the broker thus gets more commission/markup fees. This is a definite advantage to market makers.

Besides, orders are filled without unnecessary delays, and ideally, with STP execution there are no re-quotes which is another obvious advantage.

Otherwise, some brokers only offer one liquidity provider, others give traders access to a deeper liquidity pool. Obviously, the more liquidity providers there are, the better order executions.