TL;DR; It does not matter much. Either way will be about as fast.
Somewhat more detailed:
The HDD will not profit from being on a SATA III bus. Max sequential speed from a consumer SATA disk is about 100MiB/sec. Max speed from a high performance 15K RPM SAS drives on the outer track is up to 200MiB/sec. Both speeds will not even fill a SATA II connection.
A modern SSD however can use more than SATA II speeds and will be faster on a SATA III bus. THe difference might not be all that large unless you are doing sequential transfers, which is unlikely on a small SSD with the OS on it.
In practise this means you should put the SSD on the SATA III port and you might see s light speed gain. (Remember, the SATA-bus channels is max speeds, and usually not sustained speeds).
Sata3 bus speed is generally better than mechanicals can keep up with, so put the SSD on it. most mechanical hdds can handle peak data rates of 200MBps, far less than even SATA2 (300MBps) and especially SATA3 (600MBps). https://en.wikipedia.org/wiki/Serial_ATA Note that you will not be able to install windows on a 32GB drive.
– Frank Thomas – 2013-11-25T00:18:53.950@Frank I installed Windows 7 and 8 on 30gb ssds, no issues – Canadian Luke – 2013-11-25T06:31:00.387