A lot of mags will require .dng files for submissions, because they keep not only the .exif data, but everything you do to manipulate the photo- the entire history of the shot. If I shoot in RAW, I leave it in RAW.
When you import shit from your camera, LEAVE IT AS IS. When you have reason to export, decide depending on the scenario. Internet? Lower res jpegs. Mag submission? Find out what the mag wants. Sending it to your friend? Give him jpeg, his computer may not read anything else.