Which camera to buy 40d or XTI?

I am a photography student looking to go pro soon. I will be starting a photography business in the near future, shooting portraits, more studio work. My business partner and fiance have a Canon 30D. I am considering between a Canon 40D or the XTI. Reason being Canon 40D is more pro. The XTI because I'm only starting out on business and do not know what can happen,plus we have the 30d. With a XTI I can invest in a better glass as well.

That's right, the lenses make the camera. Unfortunately for Canon, this means you'll have to invest a lot to get great quality lenses. For the best, go for the L series. Otherwise, you'll just have complaints.

This is a dilemma. I hardly recommend the EOS Rebel series. The 40d is a great camera, but like you said, is much more expensive. The 30d is a great camera as well, so this will probably fill the void of a better camera. In this instance, the XTi would make a great backup body. Better yet, you might just skip another camera body completely, and buy an even better lens. It's just an idea, and if the 30d ever gives out, especially on a paid shoot, that would not be too good.

You should just buy the XTi, and a descent lens.

Hope this helps.

Neither camera has image stabilization and depends on auxillary lenses with VR which are quite costly.

Instead, check out the Olympus E-510 10 megapixel DSLR with built-in image stabilization, active CMOS LCD [found in Nikon 200/300], 3 fps onto a 12-bit RAW compact disk cards, with a 2 lense starter kit beginning from 18 mm thru 200 mm and sells for $689 [w/o CA sales tax] until Wednesday, December 12 at samy.com.

Good luck!

Far be it from me to challenge your business model, but have you compared the quality of digital portraits compared with medium format?

Any used Mamiya or Hasselblad will blow either of those cameras away.

I'm just wondering if you want to ask people to pay for images they could get from the camera they have at home.

Just my $0.02.

If you are planning to go pro soon, don't buy either of those cameras. To quality compete with the other studio professionals, you will need one of the full frame Canon cameras... EOS-1 or EOS-5 series. You just can't put out a studio quality image using one of the half frame (or less) cameras. Would be like trying to compete with another pro who uses a film Canon when all you have to use is a Minox. The smaller cameras are OK to use for snapshots at a wedding, sports pictures, or for Calendar type vacation pictures, but NOT for studio work (portrates, fasion, advertising, etc.).
That being said, the lenses you do have for your mini Canon series camera will fit on the full frame Canons unless they are EF-S series lenses, and most of your other accessories will also fit.
The image stabelization system is a myth for studio work. Most studio photography is done using strobe lite systems and the camera is almost always on a tripod so image sharpness should not be an issue if you use your camera properly. If you are shooting news, sports, construction, or other action pictures, an image stabelized lens or two is an OK investment, but not a necessity for studio work.
You certainly won't go wrong with Canon quality in your business, I have used Canon in my business for over 20 years with no regrets or complaints. I started with the EOS film series and in the last few years have switched almost completely to digital, but I use EOS 5D bodies, not the small image sensor cameras. I have had several of my customers try other photographers who charged lessmonet for their services, come running back to me after comparing my work with the less expensive results they got. I would like to think this is because of my superior photographic talents, but in most cases I discovered that my competition was using a small sensor camera and when the customer needed a good sized print for display purposes, they just could not furnish it.
Good luck in your business venture...