I use the screw-knob as well as the PCL1 clamp, which is basically a screw-knob on a rotating base. I could not be happier. Small turn and no camera can fall out but you can easily slide it in or out. Why would you want to use the lever over the screw-knob?
Personally, because I tried the old "slide out and back in from the side" trick as a means to avoid unscrewing the clamp completely to pull the camera out from the top.
I thought when securing the camera... TWICE... that it was in, when it wasn't. I realized the temptation to save 3 seconds and a couple screw rotations was too high, and after bobbling and catching the camera like this the second time, I opted for the lever clamp which is so fast it removes this temptation.
A $150 investment to save a $10K mistake... worth it to me.