I don't know much about the topic, but I recently saw a Canon 650D DSLR in action and its internal mic was really good. If I got a camcorder such as the Canon Legria R406 would it use the same internal mic components?
The mics are not all the same across all Canon products. I can't guarantee that the same mics aren't used in some different models, but I can guarantee they use more than one different mic. Additionally, even if they do happen to use the same microphone, the placement of the mic within the device as well as amount of noise the mic makes and the quality of the analog to digital converter are going to make a big difference on how it sounds.
In other words, internal sound quality is not directly comparable between devices, other than by actually recording and listening to how it sounds.