Don't really know.
I am fine if the system buys when I want to buy and sells when I want to sell. That's all I want. Clearly, brokerage and fees don't matter at all when they are already negligible compared to profits / losses.
Maybe when I think I am trading more than enough lots with existing brokers and feel the need to diversify Or if my brokers mess up (personally, not hearsay) and at the same time you don't