I own several different SATA3 speed drives from different manufacturers. I've also installed many SATA2 and SATA3 SSDs at work for our company laptops. Not the OWC drive in question.
SATA2->SATA3 for an SSD is not a jump in speed unless the SATA2 drive sucks for IOPS (not the SATA bus limitation but the drive itself) or you transfer large multi-gigabyte files.
High IOPS drives the speed jumps in SSDs. Even going from a low IOPS to a high IOPS SSD isn't going to be a night and day difference like, say, a HDD to an SSD.
The brands for SATA2 and SATA3 drives I've used:
Intel
Crucial
Kingston
OCZ
This was before I bought any Apple laptops. From my experience, I won't be buying the OWC drive unless I need the 480GB of space.