Most desks treat routing as solved: pick the venue with the best quote and send it. That holds until the clip is large enough for depth to matter.

Where the spread really goes

The quoted spread is the first layer of cost. Under it sit queue position, adverse selection, and the funding leg if the trade carries.

A worked example

A 40k USDC clip split three ways looks worse on paper and better on the fills, because each venue only absorbs the size its book can take at five basis points.

When splitting stops paying

Below roughly ten thousand USDC the extra taker fees outweigh the depth gained. One venue wins.