Suppose that your project demands high image quality and high magnification. For example, you are going to make a 20 x 24 inch enlargement and display it in a corridor where people can walk right up to it to check out fine detail. This requirement pushes you toward using a large piece of film for the original exposure. Ansel Adams would pack his 8 x 10 inch camera into the Sierra with a mule. If you're the mule and your subject isn't in your home or photo studio, think about whether you'll have the energy to take any pictures after carrying around a particular camera and its accessories.
Different cameras work at different speeds.
With the latest Canon or Nikon autofocus systems, you might be able to capture an unanticipated event on a soccer field . Ansel Adams could not have done this with an 8 x 10 view camera, which requires many minutes for setting up the tripod, focusing, stopping the lens down to taking aperture, closing the shutter, cocking the shutter, film loading, dark slide removal, and exposure. If your subject is a big mountain, you can probably afford to take your time making the image. A camera won't do you much good unless you can buy film in the right size for it. Almost every emulsion will be available in 35mm cartridges.