I'm building a PC for video editing and am wondering if there is a noticeable difference between SAT2 and SATA3. For the money, I can get 2 x SATAII drives for the price of a SATAIII.
No, the difference is tiny. The fastest "normal" SSD I've seen is around 340MB/s, which is only 40MB/s beyond the SATA 3Gb/s standard. And mechanical drives are far slower.
The fastest I've seen an SSD drive run on SATA 3Gb/s is around 240MB/s, so goes theory vs practice. But super-fast mechanical drives run around half that speed. So the difference is barely noticeable on the fastest SSD drives, not noticable on the vast majority of SSD drives, and completely meaningless on mechanical hard drives.