When it comes to videography, the most important rule is to get the mic close to the talent. Doing this will improve your audio more than anything else. The inherent quality of the onboard mic/format is far less important. Most people of course use the onboard camera mic, which usually positions the mic far away from the source (big problem!). The only solution then is to use an off camera mic, assuming your camera provides a separate mic input jack. But, at this point things get more complicated.
Standard consumer grade digital video cameras often provide an input stereo mic jack which is for unbalanced (unshielded) mics. These are fine if tethered to only a few feet of cord, but beyond that, the mic cord acts like an antenna and may be prone to picking up interference. I use a professionaly quality XLR balanced (shielded) mic, but this requires the addition of a converter box costing over a hundred bucks.
I own a Sony TRV 900 prosumer grade mini DV camera, and the audio is better than my old 8 mm analog camera. There is still a small amount of noise in the digital sound of my Sony 900 which has been attributed to a somewhat noisey preamp curcuit in the camera. So, you see some of this stuff varies from camera make to camera make, and is not just inherent to a given format. When I really need to get a superb recording, such as an instrumental audition, I often record to minidisc, then dub this onto my video in post production. Converting any of this stuff to analog is easily done in post.
There is tons of information on the web about this stuff.
Hope this helps to get you started.
John