There is only one international standard for SATA cables. There is absolutely, positively no difference between a cable advertised as SATA 2 and a cable advertised as SATA 3.
The same standard has been in effect since 2002. There are no changes. It is just another example creative advertising used to generate revenue.
Here is a link to a very interesting article about SATA cables that were torture tested:http://www.maximumpc.com/article/features/your_sata_cable_slowing_down_your_data_transfers_max_pc_investigates