Quote from loufah:
Well, here are a few places where it matters:
- You can get an extra penny or two per contract if the broker routes to an exchange that offers price improvement, like BOX. I traded thousands of SPY contracts at Schwab and never once got price improvement, because they didn't route to BOX.
- I don't know what their policy is now, but Ameritrade at one point routed orders to a specific exchange predetermined for each option series - they would not route to any other exchange. If your price was inside their chosen exchange's spread, you might not get filled, even if another exchange was posting that price or better. For example, if ISE were quoting 1.10 x 1.20 and PHLX were quoting 1.00 x 1.30 and you placed an order to sell at 1.10, if Ameritrade decided to send the order to PHLX you might see the PHLX spread go to 1.00 x 1.10 rather than having them fill your order. An Ameritrade rep even told me that, for options, they do not guarantee that you will get the best price.