How do you explain the exorbitant rollover rates of EFX as compared to 'fixed spread brokers'? When you place limit orders, how do you know what the spread is at the point of execution? Under what circumstances is trading with an ECN better than a bucket shop?
Are you talking about the spread @ time of rollover? If so it is not exorbitant it is actual. Refer to my previous post.
You can only know what the spread is at the time of execution on a limit order if you are watching the order execute, or otherwise have a means of tracking the bid/ask prices during execution (a program perhaps?)
I personally have found no circumstances when trading with a bucketshop is better than ECN (Once again if you are the average retail client)