AC97 or HD Audio?

My Cooler Master case has two options to plug into my motherboard audio connector. My mobo is a DFI 865PE-TAG. Which connector do I use? or does it matter?
http://www.hardwareinsights.com/forum/
http://www.hardwareinsights.com/forum/viewtopic.php?f=10&t=523
Onboard Audio
Audio chipset: AC97 codec