Q: My TV supports Full mode, shouldn’t I use this?
A: No. TVs support Full to make them easier to calibrate. Most TVs will not display a black level below 16 because video content should never have it. By letting you see Black 15 or 14, it can make it easier to calibrate the display and get the black level correct. However, you really should not use this as your main setting as most displays are not designed to display levels below 16, and often introduce color tints when doing white levels past 240 or so. Additionally, if you restrict yourself to levels 16-235 you wind up with a brighter image with a better contrast ratio, as you can turn up the contrast level higher. Contrast Ratio is the thing your eye notices most, and so it will produce a more pleasing image.
Also, since any non-video game content will only use 16-235, these picture settings will work for all inputs and sources, not just a single source.