Do most clients do a constant throughput or do they do bursts? Because speed does matter a lot if it's burst (send 100MB to fill a buffer, then wait). The faster you fill whatever buffer, the faster you can let another client use the connection.

Correlated, but obviously bad code can really fuck with neighbors. And each client has an incentive to be greedy so users of that client get a better experience. So you fall back again to QOS for what you care about..