I have not seen a really good direct comparison, but I had a big debate with myself as to whether to buy a D2H- D2Hs or a D2X. After very little thought and research I dismissed the D2Hs as just not being worth the extra UK's £1000. ($1850).
Next I looked long and hard at the D2X and spoke at some length to my agency. Oxford Scientific Films who are part of the Photo Library Group. Now this organisation want BIG FILE SIZES and I thought that they would advise me to buy the D2X. Surprise, surprise thay came back to me and said that there were too many unresolved issues with the D2X and said spend the money on a D2H and wait until at least a year before considering changing up to a D2X. So I bought a D2H from Hong Kong and saved myself £2000. ($3600), an amount of money that is not to be sneezed at.
I apologise for not answering your question about a direct comparison, but hope you find the above of interest.
They were in part the file sizes and the likelyhood that people would have to upgrade their computer systems to accommodate this aspect. The agency wants TIFF - RAW and a JPEG of each submission; therefore one picture, let alone 1000 would take a massive amount of space. Another was the RAW converter that was available and lastly Nikon have not been that good with the reliability of their initial releases. D70 back-focus; D2H autofocus and exposure problems, and they felt that a period of stability should be allowed before anybody went out and bought JUST BECAUSE it had 12.4MP etc.
Obviously some photographers did, but OSF did not require theirs to do it as yet, and it is this part of the group that takes my work. I therefore felt no need to spent £3500 whenh I only needed to spend £1500.
Bob I agree, I don't like to be the first one. But there is one thing for sure, any profession or hobby always requires a influx of new capitol in varying amounts. You get got one way or the other. CS Dayan