Tim scans at 4000PPI. Now, 4000PPI will give something like a 40k/30k pixel image. To match that size the IQ180 would need to be blown up almost five times linear.
I have looked at a 67 Velvia scan at 6000 PPI. Downsizing it to 3000 PPI and upsizing it I could not see any difference. Doing the same exercise to 2000 PPI and back the difference was clear. So I'd say that Tim's approach of scanning at 4000 PPI is reasonable.
What looks most reasonable to me is to:
1) Make a basic conversion of the IQ180 image using default settings in C1
2) Upres to 2000 PPI and sharpen to taste
3) Downres 8x10" image to 2000PPI and sharpen to taste
4) Analyze and draw conclusions
5) Upres IQ180 image from original to match 8x10", sharpen to taste
6) Analyze and draw conclusions
I'd assume that there will be no clear winner/looser. Digital has advantages in some areas, noise, sharpening, handling of low contrast detail. Analogue has some benefits of it's own, but they may be harder to demonstrate. Negative film will definitively handle specular highlights better than digital but may lack in other areas. They are different animals.
I'll save you the trouble, because here is the likely result:
1) If your processed IQ180 files look bad compared your processed 8x10 files, the digital folks will claim your digital processing was flawed, or that you didn't know how to optimally use the camera and/or lens and/or software.
2) If your processed 8x10 files look bad compared to your processed IQ180 files, the film folks will claim you used a bad camera or a bad lens, or bad technique, and/or had a bad lab process your film, and/or didn't know how to scan or the lab you used scanned poorly.
In short, you will spend a bunch of time and prove nothing except to yourself.
And here is the bit that seals your fate: The fact you are already asking how to best process the Phase files does not bode well for the outcome...
Sorry, but I am being realistic not pessimistic: It will be virtually impossible to perform the test in a manner that will satisfy both extremes, especially if you are not already a recognized expert in both 8x10 capture and scanning as well as an expert in digital processing using Capture 1.