What difference does it make to shoot in advanced modes such as a shutter or aperture priority versus the automatic exposure modes? Your camera is designed to make a good guess in average circumstances. It quite literally puts everything in the centre, be it the focal point, the subject or metering of light. When you set the camera to auto you are accepting the middle ground on every shot.
Much of the time there will be no difference between your interpretation of a scene and the cameras, that is true. But the point of having creative control of the camera is so you can take shots that are not ordinary, so you can spend more time away from the middle ground.
If your goal is to look at a histogram and have all the curves balanced for every photograph then maybe stick with the automatic functions of the camera. If your goal is to take photos that nobody else has imagined, to express your own character and flare, then start ignoring the histograms and ask yourself, "Who's taking these photos, me or the camera?"
There is an element of technical challenge to gaining greater creative control. In order to better drive the camera you need to learn more about it. You don't have to learn the advanced modes simply for the sake of it, there is a genuine context for each of the advanced features. If you learn these modes with a particular creative shot in mind then they make more sense.
We have a reason to get technical, for the sake of getting creative. This doesn't mean you need to become an expert on the operation of SLR cameras. Any little bit of control you can master over the camera can yield a world of creative opportunity.
The starting point for creative control is a baseline configuration for the camera. This is the default setup you select for a variety of advanced features. You can vary how you use each feature, but after deviating the configuration for a particular shot you return the camera to your baseline once again. It's a conscious process that reinforces your awareness of the camera setup, the light around you and the process of building composition for your images.
There are just three main elements that you need in your baseline – shutter, aperture and ISO. For beginners I recommend shutter-priority mode, which simply means that you select the shutter speed and the camera adjusts aperture to suit. A shutter of 1/160th of a second is good for beginners. 1/60th can still lead to blurry shots, while higher shutter speeds of 1/500 can reduce your depth of field. My recommended baseline also include a low ISO setting, which I suggest to use 200 ASA. That's good for bright light on a sunny day.
And that's your baseline. Shutter set to 1/160th, ISO set to 200 ASA.
When required you move away from the baseline. If you move out of the sunshine and into the shadows just switch to a higher ISO setting, say 1600 ASA. If you decide you want to shoot portraits with a low depth of field then switch to aperture-priority and select the minimum F-stop. Each of these variations now take on meaning as being a single step away from the baseline.
Whenever you leave your baseline it becomes a conscious act. You ask yourself, "Why do I want to move to aperture priority? Do I have a particular need for low depth of field, or greater than usual depth of field? Am I at risk of underexposing or overexposing my image at the current ISO setting?"
And before you know it you're in technical control of the camera, ready to explore more creative possibilities.
This is not a set and forget mode, that's not what we want to achieve. You still need to keep an eye on what the light meter inside the camera is telling you. If the light is too low then the minimum F-stop for the lens will be flashing in the light meter. If the light is too high then the maximum F-stop will flash.
These are the basics you need to get a handle on if you are to be in control of the camera and not the other way around.
WHERE TO START
Beginners who join a camera club may often be given conflicting advice on whether to use shutter-priority or aperture-priority. Try to remember that aperture-priority is especially useful in a studio context, where light is regulated and measured out as needed. Depth of field and having just the right amount of it is paramount.
Travellers work in a different realm, a world where light varies constantly.
Most travel photographers I know work nearly exclusively in shutter-priority, while most landscape photographers use either aperture-priority, fully manual operation or lock off the shutter with a bulb to achieve really long exposures. Every photographer has a baseline mode.
It takes a lot of confidence and experience to master aperture priority as your baseline when travelling. You can miss a lot shots trying to reconfigure your camera when the moment happens. Beginners are best to start with a shutter-priority baseline, and work their way towards the more complex technical settings.
With each new variation from the baseline you can embrace ever more creative results.