Anything you would want to do..
By the body for the lenses..
All have a decent amount of less expensive and third party lenses available. Canon and Nikon have more..
Canon and Nikon offer a better selection of high end lenses, ie. fast primes, telephotos and zooms..
Canon lenses are generally less expensive, Sony's are the most expensive..
The Sony has inbody IS that helps defer the cost on some lenses and allows the use of fast prime and macro lenses with IS..
I might throw the Olympus E-3 into the mix as well. It is the most weather sealed of the them all and the mid-grade lenses are sealed as well and generally very good and at a good price as well..
Compared to the Canon EOS-40D, the Sony also has higher resolution, higher available ISO speeds (boost to ISO 6400), super fast Autofocus (without needing a lens with a built in focus motor, thanks to a beefed up in body focus motor, AF sensor assembly and AF algorithms), all lenses stabilized thanks to Super Steady Shot..
Based on more than one recent review the A700 outresolves the 40D on test charts if you care about that kind of thing..
The A700's write speed to a fast memory card is also *dramatically* faster than the 40D (roughly 4 times as fast to a newer card like an Extreme IV), clocking in at around 28MB/Second. So, if you wanted to shoot in continuous mode (especially raw), you'd have much faster buffer flush times to media, and faster "full buffer" frame rates..
Because not as many DSLR users are looking for Minolta lenses versus Canon lenses in the used market (since Minolta was the "new kid on the block"), used lens prices also tend to be lower for many types of glass..
For example, try pricing lenses like the Minolta 70-210mm f/4 compared to a Canon 70-200mm f/4 (the Minolta lens is very nice and can be found for around $150 used, sometimes less). http://www.keh.com usually has pages and pages of used Minolta Autofocus lenses in stock at great prices..
Minolta made over 16 million Autofocus lenses with a much lower percentage of DSLR owners trying to buy them, compared to the much larger number of Canon DSLR owners trying to find used lenses from the 32 Millon Canon has made..
You can see some incomplete lists here:.
Fixed Focal Length Lenses:http://www.dyxum.com/lenses/results.asp?IDLensType=1.
The lenses I use with the Konica Minolta Maxxum 5D and Sony Alpha 700 include the Minolta 28mm f/2, 50mm f/1.7, 100mm f/2, 135mm f/2.8, 24-85mm f/3.5-4.5, 35-70mm f/4 Macro; Konica Minolta 18-70mm f/3.5-5.6; Tamron SP 20-40mm f/2.7-3.5, Tamron SP 35-105mm f/2.8; Vivitar 70-210mm f/2.8-4. All Autofocus (and all stabilized on the Konica Minolta Maxxum 5D and Sony DSLR-A700)..
Both genuine Minolta, Sony and third party lenses (Tamron, Sigma, Tokina, etc.) in this lens mount are are all stabilized on a KM or Sony DSLR, and they'll all AF faster with the upgraded focus system in the A700. Canon lenses will be limited to the speed of the lens focus motors (all AF lenses in Canon mount require a focus motor in the lens)..
AF speed is similar to stabilization from my perspective. If both are in the body, all lenses benefit from better camera body technology (and I'd be far more likely to upgrade a camera body to get better stabilization and AF speed instead of replacing perfectly fine lenses). .
There are pros and cons to any of them. If you really care about all of the tiny details, I'd wait for Phil's review to see how models like the 40D, D300 and A700 compare. But, any of these advanced amateur type cameras are capable of taking nice photos..
You're really just "splitting hairs" choosing between them, unless you have some unique requirements. I do (I love taking photos in very low light). For example, I sometimes take photos of live music in a very dimly lit restaurant, where my shutter speeds may be running as slow as 1/20 second at ISO 3200 with a 100mm f/2 and still get plenty of keepers when the performers are relatively still..
Well, Canon and Nikon don't offer stabilized primes that bright. So, I'd probably get a lot of blurry photos with another camera model like a Nikon D300 or Canon EOS-40D, unless I wanted to lug a monopod or tripod around with me when eating out listening to the live music. No thanks. .
That's the versatility part (all lenses are stabilized on a KM or Sony DSLR body including fast primes, macro lenses, inexpensive or higher quality zooms and more..
As for the Nikon D300, unless you're shooting sports and need the higher frame rate, I couldn't see spending that much money on one..
I don't see any benefits to spending more money on a Nikon solution for the types of images I'd normally shoot, especially since image quality appears to be very comparable between these cameras (as you'd expect since both the D300 and A700 are using a Sony 12MP Sensor), especially since the Nikon would give me a lot more blurry photos when I use a camera in low light without a tripod (since they don't have stablized primes as bright as I shoot with in those conditions)..
More money for more blurry photos? No thanks. I like my A700..
Thank you to everyone. A lot of good information. I have narrowed it down to the Sony... only drawback I see now is the availability of lenses for the Sony..
Are you saying that any Minolta AF lense will work perfectly on the Sony (since it came from the technology)?..
Why are you picking these three?Olympus E-500, Olympus E-510..
Are you saying that any Minolta AF lense will work perfectly on theSony (since it came from the technology)?.
Absolutely, and if you follow the links to lenses in my last post, you'll see links to user reviews from KM and Sony DSLR owners if you click on a lens model (as well as links to sample photos from a given lens that forum members posted there)..
You can also use third party lenses (Tamron, Tokina, Vivitar, etc.) in Minolta Autofocus Mount (a.k.a., Minolta A, Dynax, Maxxum, Alpha Mount)..
They would also be stabilized on a Konica Minolta or Sony DSLR..
The only lenses that you sometimes find an issue with (usually a failure to Autofocus) are older Sigma Autofocus Lenses (an even most of those work). You sometimes see compatibility issues with older Sigma Autofocus lenses in NIkon and Canon mount, too..