Canon 40D or Nikon D200 or D300? Hi, I was a serious amateur film photographer, very old-school, never owned a zoom due to degradation of the optics, knew how to find a "neutral grey" in any scene to pre-meter, never touched any kitchy soft-focus or star-filters. Never owned an autofocus lens. Was hooked on Nikon professional series film cameras until I used my mom's Canon film camera with a higher-end, faster lens which blew my mind. She gave me a Canon film body and a couple of standard lenses, but still hasn't let go of the "best" lens but may.
So now I know I want to buy the best best best lenses out there and every 5 years or whatever is required, I'll upgrade the camera body.
Currently I have a 3-year-old and my high-end point-and-shoot digital is about to drive me insane with the slow lens, shutter delay and blurry pictures.
I want to be able to focus on a person's eyeball, feel certain it's really in focus and then squeeze the trigger. I want to be able to meter a scene correctly and immediately, as well as pre-metering for the conditions such as backlighting. I want zero shutter delay.
I want to be able to buy professional-quality super-fast lenses because I always shoot in available light and never use flash.
I'm basically shooting portraits of someone on the go (preschooler).
I have waited and waited and waited until I felt the digital SLR's were "good enough." Now, I'm still floored by the prices, and don't know how I'll justify the expense, but feel I must do it.
Not knowing your budget, I'll err towards the low end which means you should get the Canon 40D. Yes, the Nikon D300 has more overall features but it's also $600+ more which isn't exactly chump change. Plus those extra features may or may not be important enough to you to hand over that much more cash.
Also, you mentioned that you wanted to buy professional-quality super-fast lenses and right now, the best route for that is Canon. Nikon's primes are lagging because of their focus on DX zooms the last few years. Rumor is that may change in the next year or two but I won't believe it until they announce it. However, also keep in mind that those "professional-quality super-fast lenses" aren't cheap. The current "holy trinity" of Canon primes are the 35mm f/1.4, 85mm f/1.2, and 135mm f/2. All 3 will run you over $3500+. However, with the 1.6x crop of the 40D, you probably won't need 2 of those 3 lenses unless you like shooting telephoto.
The 35mm is IMO a must have. On the 40D it's really a 56mm which is a slightly longer than "normal" lens but it's a fantastic lens through and through. If the price is too much, then the Canon 35mm f/2 or the Sigma 30mm f/1.4 can be chosen instead. The Sigma is excellent provided you don't wind up with a bad copy.
The 85mm f/1.2 is the ultimate indoor portrait lens but it becomes a 135mm on the 40D and frankly the focusing speed for this particular lens will be way too slow to keep up with a 3yo toddler. But if you must have this focal length, the Canon 85mm f/1.8 is a worthy alternative. It's much cheaper, focusing is much faster, and for the most part it's equally sharp. You just lose some light and a bit of smoother bokeh.
The 50mm range would probably work best for you though. The top-of-the-line lens in this case is the 50mm f/1.2 but this lens has some purported issues with backfocusing at close distances (~2-3 ft) while stopped down (f/2.8-5.6). The cheaper alternative is the 50mm f/1.4 which is a pretty good lens but some people have complained about softness and lower contrast wide open along with poor AF while in low light and the overall build quality isn't as good.
Because of the 40D's 1.6x crop, you may also want to consider the 24mm f/1.4. Not a cheap lens either but on the 40D it'll give you the FOV that the 35mm would have on a full frame camera.
Moving back to the bodies though, the D200 shouldn't even be considered at this time. It's performance at high ISO levels is miserable compared to the 40D and D300. Between the 40D and D300, the D300 arguably has an edge. But it's not extremely noticeable unless you enjoy viewing your photos blown up 100% most of the time. Plus it's nothing a good noise-reduction software can't take care of. To my eyes, high ISO noise with the D300 tend to be a little larger grained and more noticeable than with the 40D. But printing onto a normal 4x6 photo (or pretty much anything less than massive poster size) won't show any difference.
AF-wise, the 51 points that the D300 has certainly sound impressive but in real use, scrolling through 51 points can be a real pain. There is the menu option of switching to an 11 point system which is more manageable or if you're using dynamic-area AF, you can choose 9, 21, or 51 active points. The 40D simply has 9 AF points. All of which are cross-type with extra sensitivity for lenses f/5.6 and faster. The center point has even more sensitivity on top of that for lenses f/2.8 and faster. Out of the D300's 51 AF points, only 15 are cross-type and for some reason they're all located in a 3x5 grid (vertically oriented) smack in the middle of the viewfinder. If you switch down to the 11 or 9 point AF system, only 3 of those points (column down the middle) are the cross-type ones.
Historically, Nikon has done metering and auto white balance better and more consistently than Canon but that's not to say that Canon's results will be way off. Might result in a little more post-processing work if anything. But my experience with the 40D and D300 didn't reveal a massive difference in either area between the two. The photos taken may look much better on the D300's sparkling LCD but once downloaded to the computer, they're pretty much the same.
I just purchased an EOS 40D but that was influenced by the fact I already had a 10D and a number of Canon lenses. If you yourself already have a good selection of Nikon lenses that you are happy with, I would suggest you may want to stay with Nikon. Canon no longer is the king of low light photography and if you were thinking full frame and a lot more money, that the Nikon D3 would be the way to go. The Nikon D300 should be equal or better than the EOS 40D. You may want to look at the observations by Michael Reichmann and others at his website, www.luminous-landscape.com who as someone who was using Canon DSLR's was very impressed by the new Nikon entities. Also, do not ignore Sony and Pentax with built in image stabilization on the bodies.
I use the Canon 40D ($1,149.00) with two "L" lenses and I love it. (I have the 17-40 and 70-200) But, there are reviews of both camera and the D300 is a slightly better camera. But, it is a lot more expensive. ($1,799.95) Both have all the capabilities you will need. It comes down to how much you want to pay.
I suggest you buy a wide angle lens that performs well in low light. Kids are indoors and on the go all the time. If you buy the 40D I suggest getting the Canon 16-35mm-f-2.8-L. I use the 17-40 F4 and it is too slow to use indoors without cranking the ISO up to 800 or 1600.
If you buy the Nikon D300 I would get the NIKKOR 35-70mm f/2.8D.
I know these selections are expensive but you will be very frustrated if you buy slower lenses and try to take pics of a moving subject indoors. You could get slower lenses and then turn up the ISO but then your pictures will start to get grainy. It depends on how serious you are about how you want your pics to look.
I have looked at both D300 and 40D, exchanged and use them with my friends who owns 2 D300. The choice is clear---Canon 40D! Both have very similar IQ, and feel about the same in built quality. Canon actually feels a bit faster and better software layout. Nikon offers you more adjustments, but you probably won't use them much as amature photographer. 40D with kit lens 28-135mm at $1130 compare to Nikon's 18-200mm D300 kit at $2250. That's $1120 more.... You can actually own 2 40D!!! Or, you can invest on couple good lenses. Also, in 5 years, I am pretty sure any DSLR will be superior than 40D and D300. I would suggest you get the 40D with 28-135mm kit lens, and buy the 18-55mm IS lens at about $200. It's the best choice and value you can buy! Save the extra for your next professional DSLR.
I like taking photos as well but certainly not in any pro level.
I stepped up from a Canon P&S,SD800, to the 40d about 3 months ago, i then collected 24-105mm L,100mm Macro, and 50mm 1.4 all of them are excellent lenses but i found the 24-105mm staying on the body more because it's just so versatile. After shooting with the 100mm, i found that i do not shoot macro nearly as much i had previously anticpated, therefore, I put it up on an auction site and to my amazement, it was sold $80 more than i purchased it for!! When i told a friend of mine about this he was not suprised at all because he said that Canon Lenses hold up their value extremely well! And especially when amazon does not have that lens in stock at the same time i put it up on auction really helped me as well! :)
I have looked at Nikon D300 and read many reviews and comparisons and 9 out of 10 reviews gave D300 the edge, however, i went with 40D because of the price. with that price difference i ended up with a 50mm lens :)
Also, i hear that a good lens is better than a good camera body and i certainly believe that!
However, there is one thing i miss a lot which is the portability of my SD800 which i gave away to a family member. It is kind of pain to lug around all that camera gear everywhere especially since i was so used to carrying my SD800 everywhere i went. Be prepared to get a good Camera Bag such as the Lowepros and with about 4-8 lbs of gear, it may not sound so heavy but after a whole day you'll think otherwise :( Oh and one more thing, you'll get noticed a lot when you shoot with the 40d along with a 24-105mm lens, some people will think that you are from the newspaper or something :)
Last year I was taking candid shots in Cannes, France with my 70-200 lens. Everytime I would take a photo people would stop and stare where I was aiming the camera. (It was during the film festival) They thought I was a pro photographer taking pics of movie stars. Long lenses do get a lot of attention! Hope you like your 40d! I love mine! More features are great but the most important thing is your eye and ability to quickly use the gear you have.