Riveted Chain Links
If you check EK's website and catalog you find that they recommend only a rivet-type master link for all their strongest chains but allow clip-type or screw-type links for the less powerful bike applications that use lower tensile strength chains. Rivet-type links will have the same strength as the other machine-made links if peened over properly.
The concern is that the master link connection is not machine assembled and consequently is often weaker, mainly because of the lack of consistent quality assembly by the owner or cycle shop employee.
This is the same position taken by the other chain manufacturers. DID, for example, only supplies clip-type links with their low-end series chains for use on lower-power lower-weight bikes. They are not supplied (nor recommended) for their premium superbike and racing chains.
To be fair, you'll find plenty of people who have run chains with the non-riveted links with no ill effects. They don't fail easily or often, but they're not totally fail-proof either. So I guess it's debatable as to what to do.
But keep in mind that if a failed chain simply exited off the rear of the bike every time then, I guess, it's no big deal. However, often when a chain breaks the financial consequences can include penetration of the engine casing, bending the transmission output shaft, damage to the clutch slave and clutch push rod, the shifting spindle, rear wheel hugger, and the left exhaust can. It's been shown that (on some bikes) the chain wedges between the drive sprocket and the engine casing so as to stop the engine so quickly it can bend the crank.
From a rider safety point-of-view, a chain link failure, when it causes rear wheel lock-up, especially when leaned over in a corner, can be quite upsetting.
Considering what's at stake, it's hard to justify using anything but a riveted link.
