Quote from jimrockford:
It is not possible to make a reasonable comparison between a multiple market-maker, fair ECN model, like Interactive Brokers,
IB is not an ECN!!! Do you know what an ECN is?
IB does ECN style order matching ONLY among its own
customers' orders. Against its liquidity providers it is a
pass through request-for-fill system. If you put in an
market or marketable limit sell order for example, IB
will use a version of its "smart" routing to send it to the
liquidity provider with the best bid showing at the time.
Then the liquidity provider has the option of filling it or
not. Most of the time, maybe 99.9% of the time in normal
market conditions, you will get the fill. But when you need
it the most, you may not. If IB were a true ECN and your
order hit before a the market maker's cancel hit, you would
be filled automatically.
IB's smart routing is not unbiased. For options orders, when
more than one exchange is on the inside, they seem to
preferentially route to the exchanges where Timber Hill has
a big presence. I wonder if they do the same for Forex? We
can't tell because they don't identify which liquidity provider
is behind a given quote.