My standard mode is P with easy-ISO. This way, my rear dial controls aperture-speed balance (jogs between depth of field control and shutter speed selection as required, one way or the other) and the front dial selects ISO. I find this incredibly easy and fast.
However, when working with speedlights, I usually go Manual, to allow the fine balancing between foreground (flash-lit) and background (available light). I wish we had a third dial, to always have on hand the full exposure triangle...
The reason many will experience a greater ratio of keepers when working Mnual mode may have to do with these pictures being more carefully thought out and executed, not with any hidden virtue of the mode itself. Shutter speed and aperture will always be shutter speed and aperture, regardless of the selection method chosen. A good exposure, adequate to the subject, can be achieved in many ways, but the values will always be the same. Fast shutter for freezing, slow shutter for bluring, large aperture for bokeh, small aperture for big DOF, low ISO for low noise, high ISO for sensitivity. Choose the best combination of the three, and adjust overall exposure for the lighting available and measuring method used.
http://egozarolho.blogspot.com 1. Good content, good aesthetics and good tecnique. On that order. 2. Light is more important than glass and pixels. 3. In the digital photography process, software is as important as gear.