Are we comparing retail brokerage services _or_ commissions? Based on commissions there are other firms with PUBLISHED rates that are better than IBs $5.70. It is fact and does not require an IB defense. And there are still other firms with non-published rates, that will be better still. It is what it is.
And you have to look at the whole picture when comparing rates. How many of them offer FF - 25bp on futures margin & idle cash? I'm guessing none (MB is a paltry 1.5%, practically a crime). Not interested in saving pennies if I'm losing hundreds in interest every month. Most don't offer foreign markets either.