I would say anybody that has bought into the urban myth that manual is somehow magical and gives you more control. That is a line that started only in the digital age, and my guess is that it came from those that discovered that there is great money to be made in teaching photography to those that know less than they do. The mode that you use is irrelevant, as somebody has already pointed out - if all you do is go with what the meter says - then you may as well be shooting in program or full auto.

I started as some others here with view cameras, hand held spot meters, and Ansel Adams zone exposure system, and was photographing in manual for a full 20 years before Canon introduced the AE-1. So I do know how to use manual exposure, and push/pull exposure and development to bring out the tones in a black and white sheet film negative. But that was your starting point - and from there the rest was done in the darkroom. But the process translates poorly to roll film, and while I can see the potential for applying it to digital, I don't believe that most that use manual are talking about that level of control.

What is important to know, isn't what mode to use, but how camera meters work in general and more specifically how the meter in your camera works because every single camera is just a little different. I don't mean between brands or models, I mean between the exact same brand and model. For example my D300 consistently over exposures by 1/3 stop when compared to my d200. But I can go to the menu and put in a permanent override on that bias. Back in the day of film, we would buy film in large batches so we could take and test the response of that batch of film and then apply that compensation to every roll or sheet of film in that batch. Now there was no exposure compensation adjustment on the camera or the meter, so you just changed the ASA setting that you used for the batch of film. The box might say it was 100 ASA but after testing you would decide that 80 ASA was a better setting, or you might decide that 125 ASA was a better match. So that is what you would set your meter to for that batch of film.

In todays cameras - they are really more like powerful computers - and just like a computer, they are faster and more accurate in determining a proper exposure, because they have a database of lighting patterns that are programed into the meter, so not only do they meter the light, but they evaluate the entire lighting pattern against that library. You don't get that comparison happening in the manual settings. So you need years of experience under all sorts of lighting conditions to make that same comparison and come to an educated guess as to what would be a better exposure. But in the time that you are doing that - the light has changed, the subject has moved, or a whole world of other conditions that can effect exposure has happened, and you miss the shot. On top of which - today's cameras are just not designed for manual metering. Yes it's there, but take a look through an old film camera and see how bright and full that viewfinder is - and how easy it is to see the meter. Today's digital cameras - viewfinders are dim even with the fastest lens, and the settings are not easy to see or to read.

I am not a fan of shutter priority, especially with slower lens, because it does lead to an awful lot of underexposed images because many have a habit of setting the shutter speed too high for the light conditions.

I do prefer aperture priority because you want a fast shutter speed just open you lens as wide as it will go, and if that isn't fast enough then up the ISO. If you want depth of field, just close your lens down to where you want it. If I am photographing people, then I set +1 exposure compensation and meter on the face in spot metering mode. Which is also my preferred setting. Unless I am in the studio with studio strobes, you will find my camera set to aperture preferred, spot metering.

All of that is based on photographing for newspapers for nearly 40 years and having to come back with the shot. The closer I have it in camera, the less work I have to do to the image before it hits the press. Most of my stuff gets imported into Lightroom through a preset that I designed and it's good to go with little to no tweaking and it goes out through an export present that gives the prepress department what they need. I don't remember the last time I used Photoshop for anything but it's before any of the CC versions, and I think probably going back to 3.

Sunny 16 lets me capture egrets or white flowers in full sunlight without blowing the highlights regardless of the background. If I used auto-anything the camera can easily screw up.

I think that most photographers who shoot on full manual probably know what they are doing and are smarter than their cameras.

Those who rely on auto-anything are probably having to chimp a lot, check their histograms often and adjust their exposure compensation frequently. They can break that cycle with a little practice.