How Do Choose an E-Mini Broker?

As a former institutional floor trader I may be a biased towards brokers, in a negative way, because they were the bane of my existence. For nearly two decades, most of work time, and a good deal of my off time, was spent working with brokerages. I have talked with thousands of brokers calling in orders (this was before internet trading) and found most competent; but, a sizable percentage had no idea what they were doing and their miscues were a non-stop disaster.