Does it matter who fills your trade?

For liquid stocks, does it really matter whether you end up routing the order to an ECN or an MM? I know that ECNs give rebates for adding liquidity, but the benefit of this usually only really applies to heavy volume traders or prop. traders. Also, according to what I've read people are using market orders to ensure that they capture a market movement anyway.

Basic proposition is: In most cases, SMART routing through a decent broker is sufficient (best execution should be at the bid/ask).

Question is: When is it NOT sufficient? Only when "scraping pennies", or is it generally insufficient? Why would one route to a specific ECN or MM when there is usually additional cost to do so?

 

where have you read this? no one uses market orders.

 

It used to matter. But the last year or so, they're all about the same as far as fill speed. The only ones that still suck are smart routers that most brokers have.

 

I take this to mean that the ECNs and MMs directly are about the same, but that broker's "smart routing" systems are slower due to more complicated processing or comparisons?