Canon and Nikon is commonly used by professionals while Sony rarely is. I personally do not like them but they are certainly good.
for still point and shoot cameras they are comparable
for DSLRS canon will win due to lenses, features and, build quality.
dslr video on canon cameras is amazing and unmatched.
for pro level camcorders broadcast level video cameras, sony and canon are comparable.
for high end motion picture production, sony wins clearly but they are much more expensive.
when it comes to a DSLR or Point and shoot. go to the store and take an hour or so and really experience the cameras. you should find one that really"works" with you. buy that one. if you like the interface of a sony get the sony same with the canon, unless you are doing dslr video then get a canon without a doubt.
The brand of camera is not important. Go to your local camera dealer, with a fixed budget, and handle various different models. I think your only question need be, do I want interchangable lenses, or will a fixed lens (bridge camera) suit me better. Buy the one which you think is the best for your style of photography. Remember you want to be a photographer NOT an equipment junkie.