Maybe I'm in the minority here, but the 4x5" looks far superior to the Phase One to my eye (see, eg, the veins on the leaves), even with the inevitable degradation induced by the scanning process.
Yes, I noticed the veins in the leaves, and how much softer and less detailed they looked in the Phase One image. However I my first thoughts were "yes, a typical Capture One RAW conversion".
As I've said in a different thread, I don't think that the RAW converter's contribution to this contest should be ignored. Phase One's Capture One converter, at least in my experience with digital SLR RAW files, tends to reveal less detail than some other converters (e.g. ACR, RSP). So until some other RAW converters can be tried by Charles, I think the jury is still out.
But what an exciting contest!