Rudra,
You do all these multi quotes that I never get right. Hard to teach an old dog new tricks.
Well your pic does show the advantage that large pixels give in low light. This is why I mentioned Foxy's Hs. That is a crop sensor but only 4mp, so large pixels.
12 bit and 14 bit processing, perhaps Andy or Derekb can give their take on it from a Nikon perspective. I remember Foxy and I looking at the differences between compressed and uncompressed NEFs. ( Nikon term for the RAW file ) Uncompressed from a D2X these weigh in at 21mb each but compressed only 10mb. If I remember the uncompressed retained a smidge more in the white end so of interest to wedding photogs but not for me. 12 bit v 14 bit may be similar but I have not taken time to read up on it. Not sure of who has a 1Ds Mark III to beg a similar comment from.
Andy,
D3X if 24mp or greater brings other issues to the table. A bit like the move up from 35mm to M/F in the old days. Provided you have quality glass then the file will have the ability to record even finer detail. Print to the size of a house.
The downside if you want to show off your pic online is that the compression required will do the image no favours. Take a pic of a detailed subject with your D2X and top glass ( sorry not the 18-200mm ) and process and post here. Do a crop of about 1/2 the scene and post at the same image size and you will see what I mean. I have D2X images that cannot be posted as they look rubbish with the levels of compression required. Perhaps processing guru's will add a comment to that. ( I don't mind if you say I'm talking rubbish - honestly.
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Don