I have heard very few people try to justify their $150 headsets and bottom brackets. None of them has convinced me yet.

At some point the value of the thing is based on image, not product.

Is a Chris King headset really good? Yup. Is it better than any other? Considering how simple a headset is, I doubt it. It's not like they have proprietary technology or use materials no one else can procure.

The only thing a Chris King headset has which none other can have is the logo.

Are ceramic bearing bottom brackets better? Every knowledgeable person I have ever talked to and every rational account I have ever read says the benefit of ceramic bearings are obtained only at rpms thousand of time what a cyclist can produce.

Hope and White Industries seem to produce bottom brackets which work as well and last as long as any other. Shimano Hollowtech II is my personal favorite---they will not last quite as long ... but are we talking 25,000 as opposed to 60,000 miles? We are talking an eighth of the price.

Also, BBs tend to let the rider know they are failing. You won't have to walk home.

Same with headset. When has Anyone experienced, sudden, unheralded, catastrophic headset failure? It just doesn't happen.

I have the original stock headset in my 1983 Cannondale. it has never been over-tightened or run loose. I assume it will Eventually wear down, but not as quick as a bottom bracket which gets a lot more stress and a lot worse wear from silt and such.

I put a $10 FSA in my 1984 Raleigh---its headset had been run loose and tight and was a little notchy. If I have to replace it twice in 20,000 miles I will be shocked ... but shocked for $20 more as opposed to $150 I can survive.

And my bike would not be any faster, smoother, lighter, or more enjoyable to ride with $300 worth of BB and headset.

The only way for you to be sure would be to build two identical bikes with the different parts and alternate rides.

Likely, if you did that, neither part would fail on either bike, and nothing would be proven.