Why do you think Canon came with so many models not significantly different from each other with respect to their performance.
EOS-1D Mark II N
EOS-1D Mk III
The 1D III is expected to have an initial street price of $3999, though this may change. See here: [a href=\"http://www.robgalbraith.com/bins/index.asp]http://www.robgalbraith.com/bins/index.asp[/url]
Or see the Canon White Paper here: http://www.robgalbraith.com/public_files/C...White_Paper.pdf
These cameras listed above are very different. First of all, the 5D is a full-frame sensor camera and is significantly smaller than the 1-series cameras. It shoots more slowly (3 fps) and has a smaller burst count. It has a less sophisticated autofocus system. It is targeted for photographers who don't need the ultra-fast responsiveness, burst rate, or autofocusing capabilities of the 1D series. The 5D might be well suited for hiking landscape photographers, studio portraits, etc.
The 1D series cameras are 1.3x cropped sensor cameras and are built more ruggedly. They are also bigger and heavier. They shoot at high rates, have big buffers to store more images in a burst, and have more sophisticated autofocus systems. They are targeted for photographers who need this level of high responsiveness and high framerate, such as sports photographers, photojournalists, event photographers who need to capture a fleeting moment at peak action. Very different market, very different capabilities.
As for how the 1D III is different than the 1D II, look at the white paper or the review sites. The main differences are listed. If the differences don't seem significant to you, then you might as well use the 1D II.
For me, however, on paper at least, the 1D III is a big