I always wondered about the "payment for order filled" (payment for order flow?) that exists with some deep discount brokers like Scottrade. I know brokers who use PFOF will receive compensation for sending their clients' orders to a market maker for execution. So, how does that market maker make up for this payment to your broker? Does it manifest in the market maker executing between the bid and ask and not giving the retail customer this benefit? I had both Scottrade and Fidelity and although I never noticed a difference in the best bid/ask quotes, my executions with Scottrade were just terrible. I never got price improvement. With Fidelity, I frequently have buys below ask and sells above bid with market orders. Suffice it to say, I'm much happier with Fidelity. If you trade frequently or have > $1 m, stock trades are just $8 for unlimited shares.