Originally Posted by Dave Mayer

Excellent summary. Clinchers inherently feature a weight penalty, no matter what they are constructed from. Add discs, and you have a double penalty.

I'll add the inflation pressure limitations of clinchers. Inflation pressure pushes the braking tracks on clincher rims apart, which can cause a failure, when the rim splits down the middle. Yes, I've seen it. This is why clincher rims have pressure ratings, unlike tubular rims, which are isolated from inflation pressures.

And, to avoid pinch flats on clinchers, you have to maintain a minimum pressure that is close to the maximum rating. So clinchers have a narrow range of 'operability'. In contrast, in my experience, you can run skinny tubulars at 50psi up to whatever pressures at which the tire explodes. The rim is unaffected..