Here is an informal “scorecard” I recently posted at another site – some thoughts about how new Nikon and Canon products stack up against one another.:
1DSMKIII v. ? – Canon wins until Nikon (or Sony?) announces a very high MP FF body
1DMKII v. D3 – Purely on features, I’d say the Nikon wins. The difference in fps is pretty inconsequential, but the D3 wins on most other counts. Of course, in the real world, both of these cameras are extremely powerful and very well suited to the sort of work they were designed for.
5D v. ? – Canon wins since it is the only company with a FF body in the sub-$3000 (more like mid-$2000) price range. While it lacks the speed of the more expensive cameras, it is extremely well suited to the needs of many photographs for whom image quality is paramount.
D300 v. 40D – A slightly awkward comparison since the prices are significantly different. On features, the D300 beats the 40D. In a sense, the D300 is today’s camera, while the 40D would have been an outstanding product introduction… last year.
A few words of explanation…
1. I don’t really place much stock in which camera/manufacturer “wins” or which product is “best.” I really believe that the determination of “best” has more to do with the photographer’s needs than the intrinsic qualities and features of the products produced by top-tier manufacturers.
2. Any advantage that one manufacturer has over the other is likely to be temporary.
3. All of the cameras included above (and others not mentioned) are excellent products, and all can produce fine photographic results.