Should I use SATA 3Gb/s or SATA 6Gb/s cables? I read that if I want my SATA 6Gb/s drive to perform at its rated speeds I need to use a SATA 6Gb/s cable.
Almost all SATA cables will give you the same performance, THEY ARE MADE THE SAME. The only thing that determines speed is from the board and controller of the SSD/HDD.
This is even stated by the SATA people themselves.
From the SATA document on Revision 3.0:
"SATA Revision 3.0 was designed to facilitate a much more elegant – and cost effective – migration to higher data rates. Rather than completely redefining the spec, SATA Revision 3.0 achieves its data rate increase by faster signal switching. While this has resulted in changes to the PHY, modifications to the protocol have been kept to a minimum. In addition, SATA Revision 3.0 is backward compatible so that the same connectors and cabling used for SATA 3 Gb/s under SATA Revision 2.6 can be used for SATA 6Gb/s.
This decision not only enables end-users to retain their existing investment in cabling when moving to SATA 6Gb/s, it also enables silicon manufacturers to maintain much of their existing IP. Except for the doubling of the data rate, SATA Revision 3.0 is no more complex than SATA Revision 2.6 from an electrical perspective, and no heroics are required to implement the technology at 6Gb/s speeds."
Here is a test done my Maximum PC verifying this.