OK, I'll bite.
I have listened to the Grace F9E on my system, with Audire powered, B&W 803's with B&W DM 16 woofers for subs (recently replacing, for now, Peerless 850146 aka NHT SW2Si) subs powered by a second Audire amp and preamp with a physical, rather than electronic sub filter, for now... again.
I have owned a Supex 900 since new in about 1979-80, and it has been "retipped" from a 900 E+ through 900 E+Super, to it's current 900 Mark IV. Since I used to play a lot of vinyl, I bought a Yamaha MC-9 to use while the Supex was being replaced, and I use it more than the Supex now to save what is left of the MK IV stylus for special records, especially Direct to Discs. I also still have my V15 Shure, which does not compare on my system, but it really SuperTracks! TeeHee. In fairness, the V-15 does give out a mellow, non-threatening sound and doesn't seem to add anything unwanted. It just doesn't move me. Tone arms are a Formula IV for MM, and Signet with removable wands for MC, all stuff of the Grace vintage. I also have a Grace 707 arm which works quite well.
How do these others compare? Supex first, by far, especially in the bass and extreme high end, such as the triangle in the D to D recording of Sandman on the Dixie Direct "Rosie O'Grady's...." album and also in the shimmering of cymbals when compared to all but the Grace, which is close here.
The Yamaha beats the Grace everywhere but in the extreme high end, where it seems muffled. In fact, turning up the sound reveals why it was muffled...by design. It isn't that good up there and has a brittleness that is annoying. Otherwise, it is a bit cleaner and has a much better separation of instruments in space than the Grace, but not as good as the Supex. Ther Yamaha is a boron cantilevered Fine Line stylus, if I remember correctly.
A buddy brought what was then the top of the line Audio Technica MM to show off. Frank Zappa's compelling piano intro to Uncle Remus all but disappeared into the background. The Grace does very well here, with the Shure in between. The Yamaha is still a bit more forceful on this in-your-face piano. solo, but not up to the brilliance of the Supex, at least ON MY SYSTEM!
Still, The Grace is the best MM I have ever heard, certainly superior to Grado I have heard, but I am an MC guy and probably have missed a lot.
That does not mean I think it is worth anywhere near the money people are asking for them. I considered keeping the F-9, but I sold it to send my Supex to SoundSmith.