They are both good clutches. We have only seen one problem with the HKS and it was a friend of mines car who purchase the clutch used and the pins in the pressure plate started backing out causing it to start to come apart. Other than that the HKS' we have seen held 4-500 hp just fine. I would however go with the tried and true exedy twin. Shoot me a PM if you need to pick one up at a good price.
the SD twin is a almost stock feeling pedal and will hold around 450 ftlbs well. the HD twin is a heavier pressure plate with a stiffer clutch and is rated slightly higher clamp load than the SD. You cant go wrong with either one
Justin
NC Black Beast-570whp-466ft/lbs stock block, head, ecu going under the knife for a custom FFP everything!!!
03 EvoVIII-6765 FFP block, FFP Head-580whp baseline on pump
03WW VIII-FFP block, BR Head, AEM, 35R-605hp
Force-Fed Time-Attack/Road Course "Street Sweeper"- FFP block, FFP Head, 5857*numbers coming soon*
Running The Streets of the Carolinas