I assume there are people faster and smarter than me. the fat middle is where I make money.I never do market orders, it's always limit or some kind of pegged order. So, broker fee is as important as any other transaction cost.
Long while back I was an execution quant at a desk where we would buy the volume from the TD like brokers. TDs are the the feed for HFTs. If you go through these fixed price brokers, you are the feed stock for smarter players through market impact. Does TD provide you info about market impact of order through them vs other brokers? This is very important if you have high volume trades and you are executing in chunks. You might feel false euphoria about your mid spread fills for marketable orders while not realizing that when you put the order for higher percentage of ADV, you had already moved the market unfavorably.
ps i don't assume. I know.