Here's the basic argument: On a fast boat, as the boat surfs and the boatspeed changes, the measured AWA will change dramatically. You don't want the helmsperson chasing these AWA changes, so some feel that people steer better to a TWA target on fast boats. However, if you use TWA as a target, you also need to watch your target boatspeed (BS) to prevent an inattentive helmsperson from sailing along at the target TWA, but too slowly and with the AWA far too deep. This can be a stable state and the boat can stay at target TWA, but continuously sailing far too slowly, and never accelerating to the downwind target speed. So, when steering to target TWA, the helmsperson needs to watch the target BS and be sure to sail hot of target TWA until the boatspeed reaches the target BS, and then bear off to target TWA.