As far as picture quality - I could see no difference while viewing sample photos from each camera of the same subject.
PCWorld magazine (Jan 2005 issue) had a reliability article which included camera manufacturers. They included Problems, Satisfaction, and Ease of Use.
For Satisfaction, Canon is better than Nikon. Canon and Nikon were equal for Problems. Nikon was rated Worse Than Average for Ease of Use.
Of course this is for all types of cameras, not a specific camera.
Here is a review of the Nikon 4100:
Which one produces better quality picture and more reliable? I like Canon A75 but a little hesitant now after I read the comments posted by a few people who have experienced mechanism problems with the camera within the first year.