I would ask if your turntable is in the same room with your loudspeakers. If it not, I would think that a more massive plinth might damp some of the motor vibrations.
If it is in the same room as your loudspeakers things get a bit more complicated. If there is no plinth, there is no plinth to become excited by the sound waves from the speakers. On the other hand there is no mass to sink vibrations from the motor unit.
Personally, I would go with the skeletal plinth in this situation, particularly if using a transcription length arm as that puts the tonearm mount much further from the motor unit and hence the source of vibration.
If it is in the same room as your loudspeakers things get a bit more complicated. If there is no plinth, there is no plinth to become excited by the sound waves from the speakers. On the other hand there is no mass to sink vibrations from the motor unit.
Personally, I would go with the skeletal plinth in this situation, particularly if using a transcription length arm as that puts the tonearm mount much further from the motor unit and hence the source of vibration.