Thanks for the input. Sounds like this might be something measured in micros. I did find it interesting though that the IB rep mentioned it (which led me to believe it might be a more significant difference).
That might well be the case but no broker, which is the first point of contact from the perspective of retail clients, just forwards the FIX message if it comes from clients. It usually is newly constructed to fit the specific requirements of the agreed protocol of the execution venues engines. So, if a message via API can be serialized, sent, and deserialized faster than a FIX message (and there are technologies that are faster at doing just that than even the most performant FIX engine), then an order via API can very well reach the targeted execution venue faster than a FIX message.
I was up late and didn't feel sleepy yet so I went impulse shopping on Amazon for a trading book. Saw some interesting stuff by a gentleman named Dr.Howard Bandy. Went to his site and it seemed legitimate. Not slick but honest and forthright. Then I went to ET to see if anybody else bought Dr. Bandy's material and holy @#@!, I found this thread. Fearing that I'd just been taken in an elaborate con where an elderly man creates a fictitious online persona and imitates a 70 year old computer science professor, I furiously google searched. I immediately contacted Amazon customer service and they tried to allay my fears with comforting words about a "30 day return policy." But my heart was racing, and a mystery was afoot. And lo and behold my google searches revealed... https://issuu.com/plu-archives/docs/1988-1989_catalog_of_pacific_luther/126 Dr. Howard Bandy was head of the computer science department at Pacific Lutheran University. The mystery of the dastardly computer science professor has been resolved.