On-One Inbred SS Disc Balloonbike

Stronger clamping force compared to open cam.

From Sheldon;

Despite the marketing hype associated with these "boutique" skewers, they are actually considerably inferior in functionality to the traditional type. They are often seen under rather prestigious names, as was the one photographed here. (I Photoshopped the logo off, so as not to pick on one particular brand.)

The exposed cam cannot be kept as clean and well-lubricated as the shielded one can.

In addition, the exposed cam has a larger diameter, (typically 16 mm vs. 7 mm for an enclosed cam) so the friction is acting on a longer moment arm (the radius of the cam.)

The result is that the exposed-cam type provides very much less clamping force for a given amount of hand force on the lever.