I performed direct comparisons several years ago. Both racks have improved since that time I am sure so not sure how accurate this is to their current forms, of which I still have the Stillpoints in its current generation.
The Grand Prix I had at the time had the Formula shelves and upgraded carbon fiber bearing feet under the rack. I did not have the amp stands at the time so this is fwiw.
I found that the Stillpoints and GP stands were very close in overall character with the Stillpoints rack allowing the system to sound more open in the upper octaves, more effortlessly dynamic with slightly improved low-level detail retrieval. The GP imbued a slightly darker overall tone but was not the worse for it just different. I was within a few months of needing to replace the neoprene pads under the G.P shelves though so I am not sure if this made any substantive difference.
I did find there to be a significant difference in replacing the standard shelves on the G.P with the carbon fiber Formula and an even more striking improvement when replacing the same type of acrylic shelves in the S.P with their tri-pod stands, eschewing solid shelves altogether.
One thing is certain. In both cases the standard acrylic shelves, while they might look nice, really held back the performance each of these racks is capable of without them. The differences in replacing the acrylic shelves in both cases was enormous and affected _everything_ positively. Both racks are exceptional in their own way and were dramatic improvements over my older JustaRack with double thick MDF.
I think either would perform well in most HE systems. I still have and enjoy the Stillpoints rack system and use their quad-arm stands under my amps--which was a dramatic improvement over my high-mass corian plinth sand boxes of yore.
Grant
Shunyata Research
