Normalmente, nada mudou entre os cabos entre SATA I, II e III. Do documento oficial SATA-IO:
The same cables and connectors used for current SATA implementations can be used to connect SATA 6Gb/s devices. SATA-IO recommends utilizing quality components to ensure data integrity and robust operation at the fast 6Gb/s transfer rate. Cables already at the threshold of 3Gb/s operating margins may experience lower performance than expected at 6Gb/s due to an increased number of resends.
Você pode conferir alguns benchmarks aqui .