Which is faster?

Solution
Today's HDDs can achieve sustained transfer rates of 210MB/s. That's faster than SATA I but less than the limit for SATA II.

The OP really needs to consult the manufacturer's datasheets and product manuals.
No. Sata is a bus. think of it as a highway with a speed limit. Just because you raise the speed limit doesn't mean your car can go any faster. Event he best HDD under optimal conditions don't break Sata I let alone II or III. So rotational speed determines the actual transfer rate as well as seek times. And with HDDs faster is better.