The best way to compare the standard C9.25 vs the Edge optically is to look at the spot diagrams. Celestron gives those spot diagrams in it's White Paper HERE. On page 5 you can see the difference in star shape out to about 20mm off center. Just for reference, the largest diameter 1.25" eyepiece is going to be about 27mm in diameter (13.5mm center to edge).
I've considered the C9.25 many times but that size never made sense to me since the C11 is only a couple of inches longer and weighs only 7 lbs more than the C9.25. Moving up to the C9.25 or C11 is going to take more effort either way.
With Panoptic eyepieces (68° AFOV), the views through a standard SCT can be quite spectacular. Panoptic (or equivalent AFOV) eyepieces limit the damage at the edges of the FOV making the standard SCT much more pleasant to use.
I personally don't give much credence to the 9.25 vs 11 or 8 mystic, so that's not a factor for me.
As far as your choice is concerned, it guess it depends. I personally like the Edge optics because I don't have to place the object I'm looking at dead center in the FOV to get a clean view. The Trap in Orion looks just as good off center a bit as it does on center with the Edge. With the standard SCT, it's more important to keep your object near the center of the FOV.
I'd like to resurrect this old thread and share some insights.
No mystique at all on the C9.25 vs. C11 vs. C8 standard SCT front. It's simple math. The C9.25 primary is f/2.3. The C11 and C8 have f/2 primaries. At those fast ratios, a 0.3 stop difference makes a material impact on uncorrected field flatness. Credence isn't necessary when we have science.
And be careful with the spot diagrams in the white paper. The don't specify what aperture SCT they used to get those spots, but it cannot have been the C9.25 since no-one makes a coma-free non-Edge SCT. The spots for a C9.25/C9.25 Edge will differ from the spots for a C8, C11, C8 Edge or C11 Edge because the C9.25s' primary is significantly slower and the field - corrected or otherwise - is natively better.
As for size C11 vs. C9.25, having owned both (standard C11 and Edge C9.25) there's a big difference in mounting and handling. Length is similar. An extra 7# takes you from well within the capacity spec of many mid sized mounts to very upper limit of most mid-sized mounts. Second, the C11 is MUCH fatter. Harder to hold when positioning in the saddle, takes up more cargo space and storage space, etc. I've used them both on a Takahashi EM-200. The C9.25 is much, much easier to live with logistically than the C11.
Of course C8 to C9.25 the same argument applies in favor of the sveldt C8. There's probably no more convenient 8" design for travel than the C8. It rides easily on a light duty mount (CG-5/AVX) which neither of the others do, in the case of the standard C8, costs very little, and delivers aperture that's nothing to sneeze at.