It's a common belief that the most professional way to shoot is in manual. But while Manual exposure gives you more control, it might mean missing important shots. Aperture Priority or Shutter Priority modes are often flexible enough to give you control over depth of field without the worry of making a lot of adjustments. These "semi-auto" modes can give you the ability to focus on composition and surroundings.
This article by photographer and blogger Paul Indigo offers some great reasons on why the partially manual modes can sometimes be more effective than a fully manual mode in getting you the shot that you want. He says, "Letting the camera do the technical work frees you up to be creative and concentrate on the important part, taking pictures."
In short, if you have less to worry about, you'll probably end up with better shots. Simple, but a good thing to keep in mind.