Can't go wrong with either. The one thing I've noticed is that SW mid-pipes are not available seperately like the Kooks mid-pipe. They may be available through SW, but are not listed anywhere. If you ever wanted to switch from catted to non-catted mids, the SW would have to be cut and altered to do this. Kooks has both catted and non-catted mids available if you want to switch, and simply bolt on.
I went with the SW mainly for the cost savings & they are beautiful. Maryland Speed has them for 10% off every once in a while & they were on SW fast build schedule. Only took me 8 or 9 days to get them from the time I ordered. Would need to check SW website & see if they still are.
Anything keeping you from American Racing Headers? They are high quality headers with primaries that they try to make as equal in length as possible without introducing radical bends in the tubing. Not to mention ARH is a take-off from employees at Kooks.
If you want to save the coin, I'd go SW. If you have an extra couple hundred bucks, go ARH.
All are great choices. They all use the same grade stainless steel, just slight variations in design. There probably wouldn't be enough of a performance difference on a dyno to sway me one way or the other. There definitely wouldn't be any difference according to my ass-dyno. Just pick-n-pull.
Personally, I'm just not a fan of AR headers. I don't like the fact that they're not equal. The drivers side makes a turn with the tubes, then there the collector. The passenger side goes straight back like the Kooks and SW's do. They do that so they can put the crossover pipe infront of the trans pan. I don't think it makes that much of a difference IMO where the crossover pipe goes. The Kooks crossover in the middle of the pan and the SW's crossover at the rear of the pan.
It's true we can't use the AR's with our turbo kits.
I have been running the SW's for 3 years now. Love them. I will say this, watch out for cracks. Granted I had an old set, I don't know if anything has changed in their manu. process. I was getting some ticking sounds and we replaced my gasket only to still have it. When we did the turbo kit, that's when we found the cracks in the welds. A simple weld around the outside and all has been good. They do offer a LifeTime warranty but we managed to fix them in about 30 mins.
I would say with the Kooks, you get what you pay for. BlownWK's were fantastic looking still when we removed them for his turbo install. Any set you buy are going to all make about the same power. I don't really see one set making anymore power than the others. I would love to see one of them prove me wrong.
Would I buy the SW's again..... yes I would. Like I said, I've had them for 3 years and they still look great. Other than a few cracked welds, they're still rockin'.