If your video camera can shoot in native 16:9 (widescreen) aspect
ratio, use that setting. Black bars will appear at the top and bottom
when viewed on a normal TV (4:3 aspect ratio), but you will be forever
grateful you shot in widescreen several years from now when all TVs
are widescreen. Why? Because anything shot in standard 4:3 aspect
ratio will appear with black bars to the right and left of the picture
or it will have to be stretched, which makes everyone appear short and
fat. I know many of you out there don't want to trust us on this, BUT
TRUST ME ON THIS! Or you'll be sorry.

There's more information about widescreen vs. fullscreen at http://www.shootinggoodvideo.com/widevsfull.htm