Any Gigabyte mobo users here? (GSATA question)

Hi all
 
On my Gigabyte mobo (a P67A UD7, but I think this applies to many Gigabyte mobos) there is a pair of GSATA controllers alongside the SATA3 and SATA2 controllers, the difference being that the GSATA controllers are connected to 3rd party (Marvell) chipset rather than the Intel chipset.  My only question is why are they there?  Are they to give a higher performance option or are they maybe just 'extra' controllers with lower performance? Or is there no difference in that sense?   
 
If I was going to reconnect all drives, how would I decide between the GSATA or SATA controllers, assuming I had 2 SATA3 HDDs (one for OS and apps, one for data) and a CD/DVD drive to connect?
 
I've googled on this and asked on a tech forum, read the mobo manual, looked at Utube vids etc etc but apart from a couple of things implying GSATA should be chosen after the SATA controllers I can't find anything. 
 
Thanks for any advice.