Panther Point has 6GBit/s ports. There is zero reason for Apple not to utilize them. I know this is not a perfect answer but this is all I can help.
SSD is much faster on USB 3.0 than a HDD. I would recommend reading this -- disregard the UASP part, it still gives you lot of benchmarks of running an SSD over USB 3.0. You can clearly see speeds well above 200 MB/s. There is no mechanical (notebook) drive that can do much more than 100 MB/s. Not the Savvio, not the Spinpoint M8, nothing. It simply doesn't and cannot happen.
Edit: StorageReview mentions this Hitachi DeskStar being the fastest mechanical drive of all and it barely clears 150 MB/s.