Peter, this may be too simplistic for the type of response you are looking for. Based upon years of playing vinyl and using both weights and screw-down clamps, here are my observations.
Weights - faster and easier to use. Main concern is for any affect of the added weight on the spindle bearing, depending on the mass of the weight.
Clamps - ability to adjust pressure when considered for flattening a warped or dished record. I've experienced times when over-tightening a clamp can cause the outer edge of the record to lift up, thus requiring a reduction in pressure.
I can't say I've heard sonic differences between these types of hold downs, so long as they result in appropriate pressure to produce full contact of the record with the mat.
As a practical matter, the profile of either type of hold down can endanger some cartridges when they are allowed to move to the end of the run-out groove. The screw down clamp with my Kuzma Stabi was designed to minimize this concern.
Weights - faster and easier to use. Main concern is for any affect of the added weight on the spindle bearing, depending on the mass of the weight.
Clamps - ability to adjust pressure when considered for flattening a warped or dished record. I've experienced times when over-tightening a clamp can cause the outer edge of the record to lift up, thus requiring a reduction in pressure.
I can't say I've heard sonic differences between these types of hold downs, so long as they result in appropriate pressure to produce full contact of the record with the mat.
As a practical matter, the profile of either type of hold down can endanger some cartridges when they are allowed to move to the end of the run-out groove. The screw down clamp with my Kuzma Stabi was designed to minimize this concern.