Besides the "feel" of how quickly an order gets filled in different circumstances, how substantial is the difference? Is it a matter of how well a broker can get updated on the NBBO?
I always wondered why everyone strives to get rid of the middle man yet in trading you can't live without them
I will comment on the options market: There are over 1.1 million US equity options. The average bid-ask spread on these securities is OVER $2.00. Given that the average minimum tick is around .05 - that means there is at least 40 price points between the bid and ask on the average equity option. A trader needs to understand how to enter orders in order to find the "hidden" liquidity that is constantly present between the bid and ask. You should not be satisfied with the NBBO.
it might change, but yeah, the SIP shows you the best round-lot BBO, there could be oddlot liquidity within the bbo https://www.tradersmagazine.com/dep...s-ii-an-odd-solution-for-the-odd-lot-problem/