I was looking into the new 1TB cav. Blacks and I was wondering if I have a board that only has SATA 2 on it would I get any advantage of buying a the SATA 3 drive. ie. Would the bigger cache be worth the price difference or should I just stick with the SATA 2 drive.
you will NOT have any improvement so go and buy a SATA 2 hard disk.
And I want to say more: you will NOT have any improvement even if you had a board supporting SATA 3. This because hard disk have mechanic components (that is are not SSD) and even if you had the fastest SATA 2 HDD their physical limits makes them unable even to fill SATA 2 bandwith.
The price is about the same for both drives, so no point taking the older one. The SATA 3 drives consume less power, have an updated firmware, as well as bigger cache.