Quote from jack hershey:
In a short while, as you learn, you will find that all the expenses of trading are trivial compared to the extraction you take from the huge pools.
One test of good displays is how fast their programers can improve their platforms based upon your directions. For example look at how you can interface the snippets we have provideed to the whole field of providers and secondly notice how many of these ideas have actually become part of the libraries of the providers.
Lastly, look at the private library service capacity of the providers. See if they provide super export/ import services so you can run your ATS component off their service and get back on the service display promptly. On some platforms this capability is called, in programmer's parlance, a global variable capability.
Footnote: you will also have to assess the cleanliness of the data feed. Most are very very subpar.
One of the CW general beliefs you will come to know is that most people have never seen the markets in operation. Acquire that belief ASAP.