I've used an HRS platform, Stillpoints cones, Finite Elemente Ceraballs and Cerapucs, and Equarack footers. The only isolation devices sitting under all my equipment are the Equarack footers and the HRS platform (AS turntable only).
IMO, an isolation device should and must be able to control mechanical vibrations from your speakers, airborne energy and vibrations from the audio equipment itself. And it should do all this efficiently, meaning the device itself should be optimized for the weight and mass distribution of the equipment.
HRS platforms are designed for a specific wight range, but do not take into account the mass distribution of the equipment. This should not present a problem since the platform itself is mass loaded.
SRA platforms are designed for the weight and mass distribution of the audio equipment. I don't have experience with these platforms and racks, but I've gone through all their technical information and it all makes sense to me. The only drawback I see is with change of equipment as each platform is sized based on the footprint of the audio gear that it supports.
Equarack footers are customized for the weight and mass distribution of the audio equipment via viscoelastic pellets capable of supporting up to three lbs each. With a simple first-grade-math formula, the user determines how many pellets each footer should have, hence optimizing each footer for supporting a specific wight. This is a similar approach to suspension design for automobiles.
The footer surface that gets in contact with the audio equipment is also a viscoelastic material. This is to dampen vibrations from the equipment itself and airborne vibrations that affect the surface and structure of the equipment. Under the lower face of the footer, there is also another viscoelastic disc that makes contact with the equipment shelf. This should take care of any mechanical vibration that comes from the shelf where the equipment sits on. Two aluminum discs interface with the different viscoelastic layers.
I now have the Equarack footers under every piece of audio equipment I own, except for the Acoustic Signature turntable, which sits on an HRS platform. The sound improvement that these footers have brought in far exceeds their ticket price. The sound improvement is equivalent to going from NTSC broadcast to HD broadcast. With the Equarack footers, everything sounds crystal clear. Acoustic instruments really sound like there is somebody in the room playing, voices have a palpability that I thought can only be achieved coming fro 20K audio gear and the highs are simply pristine.
I think that in order to really appreciate what the audio equipment really sounds like, one should make sure that vibration energy is under control and that clean power feeds all the components in the audio system. Many of us go out and spend the big bucks in trying to get better performance without first having an efficient infrastructure for the audio equipment. Unfortunately, I learned this the hard way. I had known about the Equarack footers for a while, but only decided to give them try at the end of last year. With these footers, I can now hear the character (or lack of character) of each audio piece in my system.
I hope this helps.
Regards,
iSanchez
Disclaimer: I have no affiliation whatsoever with any of these companies mentioned above, including Equarack. I just happen to be knowledgeable about structural design and work along mechanical, civil and structural engineers.