I think you are oversimplifying. In the US you can compete on price at a subpenny level by posting at an exchange with inverted (taker/maker) pricing. Shares po

I think you are oversimplifying. In the US you can compete on price at a subpenny level by posting at an exchange with inverted (taker/maker) pricing. Shares posted at BYX are really $0.004/share cheaper than BZX, and most smart order routers will take at the inverted exchanges first. Also, changing the tick size won't eliminate the race to 0 (or c) because there are other advantages to low latency execution beyond just getting good queue priority at the inside price. One obvious example is quickly canceling or modifying your orders when the price of a related instrument moves.