Canon or Nikon?
or Olympus or Sony or Panasonic or etc?
For the beginner photographer and even the advanced non-professional photographer, the camera body actually makes little to no impact on the final photo. Unless you're shooting for a billboard print, whether your camera body has 14 effective megapixels or 6, a full sized sensor or not is not going to make such a big difference since you'll likely be scaling down the photo for display anyway. And the brand of that camera body is of even lesser concern. This claim will be analyzed in further depth in the next chapter: camera comparison - does your camera really matter?
The brand of the camera comes into some concern when considering lens and accessory compatibility. Canon and Nikon simply have a much wider array of lenses, flashes, and other accessories to select from. But for the beginner photographer not looking for a camera with exchangeable lenses or speedlights, this should pose no problem.
popular Nikon and off-brand lenses, flashes, and accessories for Nikon
popular Canon and off-brand lenses, flashes, and accessories for Canon
At the end of the day, you're looking to buy a camera, not a brand. Each brand has its share of great cameras and complete duds. Don't fall for branding. Do your research on the cameras you want based on the features and capabilities you want. Make your own decision about which camera is the right one for you regardless of brand.