Not sure what you are asking. The 13 and 15 models have SATA III speed in the Hard drive bay...only some have SATA III in the disk drive (not
sure which production period).
The base HDD will not feel any faster because the hard disk speed is based on size, density, and RPM.
But if you are asking whether you could use a SATA III/6 gbps drive in the base mbp 13, then the answer is yes.
Hope this helps!