For many years, clips were the only choice for master links. If you look at the design, it is somewhat like a circlip that fits over a groove on a shaft. Circlips are used successfully in many rotating applications to hold components on shafts etc. I think in the application of chains, the clip can be stretched if not installed properly. When this happens, it looses its retaining abilities and can pop off. So I think the design is adequate but one has to be careful during assembly. It is interesting that every chain I buy now for my street bikes has the rivet type design. For sure it is a more secure way to hold the masterlink together. The dirt bike chains still use the clip.
As a side note. I have had one chain come apart in the 40+ years of riding bikes. It was a rivet chain on my ST4. The front sprocket clip wore out and allowed the sprocket to move back and forth on the drive shaft. As the sprocket moved to the outside, the outside of the chain began to grind on my clutch slave cylinder. Eventually, the rivets ground off and I lost the master link plate and the chain dropped completely off the bike. Luckily I was just leaving a stop sign and no damage occured. The really scary thing is that two days earlier I was heading back to California across Nevada (Hwy 50) at very high speeds. If the chain would have let go at those speeds, who knows what would have happened.
CHANGE YOUR FRONT SPROCKET RETAINERS WHEN YOU CHANGE YOUR CHAINS ON THE OLDER DUCKS!
Mike