To get back to the real and sensible reasons for choosing a camera; the quality and range of available lenses.
I'd like to expand upon an earlier comment I made a few pages back, namely:
The 24-120 F3.5/5.6 VR seems a bit below par. The 80-400 VR is no better than the Canon 100-400 IS; maybe not as good. The AF-S 70-200/2.8 VR is a fine lens; at least the equal of the Canon 70-200/2.8 IS, but it's way too heavy for me. The Canon 70-200/F4 IS appears to be a slightly sharper lens (than both the Nikkor and Canon 70-200/2. and is both cheaper and lighter. If I were to buy a new lens at this stage, that's the lens I would buy.
The new Nikkor 70-300 VR seems useful and the right weight, but alas! it's really only a good quality 70-200. Performance at 300mm seems well below par.
It occurred to me that maybe the Nikkor 70-300 VR might be useful as a 70-200 lens. Perhaps I could simply ignore the extra reach to 300mm and pretend it didn't exist. So I compared the Canon 70-200/f4 at 200mm with the Nikkor 70-300 at 200mm and F5.3, at Photozone. I added just 5% to the Canon LP/PH figures to compensate for the additional pixels of the D200 test camera used for the Nikkor lens (as opposed to the Canon 350D for the Canon lens). That's a very conservative figure.
Alas! The Nikkor still doesn't make the grade at 200mm, compared with the Canon at 200mm. However, the Nikkor is good at 70mm. I don't want to give the impression that I am in any way biased towards Canon you understand, so I'm always willing to give credit where credit is due.
Now, I can sense some of you getting a bit hot and bothered under the collar. You're probably thinking, the Nikkor 70-300/F3.5-5.6 VR is a budget lens. It's cheaper than the Canon 70-200/F4 IS. What do you expect?
And you are right. It is cheaper. But what's the alternative? A very heavy and more expensive Nikkor 70-200/2.8 which is actually not quite as sharp as the cheaper and lighter Canon 70-200/F4 IS?
Do I buy a D3X on the basis that I can save money by buying cheap Nikkor lenses which might well be good value but are optically mediocre? I think not.
Do I sacrifice this wonderful technology of IS or VR so I can use a sharper lens at a less sharp shutter speed? I think not.