Ultimately, you're talking about draining energy from the bearing/platter interface in this discussion. In this regard, the materials chosen are as important as the actual mass.
There are different ways to solve the problem, or alternatively, to screw things up.
For example, high mass with ineffective energy transmission (stores energy) is going to have a resonant signature at some frequency. It will be the mechanical equivalent of a capacitor having a high dielectric coefficient with resulting blurring and resonance. Low mass done poorly can be equally compromised.
As is typical in audio, it's the design/implementation of a particular architecture rather than the chosen architecture that makes the most difference.
All of my experiments have shown me that in a non-suspended design, high mass done right has an inherent advantage, but it needs to be noted that this is the path I've been led down, so I have a bias in making this statement.
The unfortunate reality (in terms of arriving at shared, transferable, reproducible results) is that you need to consider the experiences of SP-10 owners in the context of their entire system, their setup, and of course, their turntable shelf/stand.
I like to think a of the shelf/stand combo as a part of the turntable and try to be very careful in drawing conclusions because of this.
Context is everything, but you all knew that ;-)
Cheers,
Thom @ Galibier