Some general information about pre-loaded Styles:
"Standard" is told to emulate Kodak's Ektachrome 100 slide film emulsion. Also the "Portrait" and "Landscape" styles are told to emulate popular film emulsions.
"Neutral" is told to be tweaked to maximize the amount of information transfered to the RGB output (JPEG / TIFF file) and is therefore indicated for JPG shooters and RAW shooters who use DPP for RAW conversion only but do the remaining post-processing e.g. in Photoshop.
"Faithful" is told to be the closest to the human eye response. It seems to use the same tonal curve as "Neutral" but color tones / satuation are different.
Some personal notes of mine.
Picture Styles affect the JPG thumbnail embeded in RAW files and the histogram displayed by the camera. There are some threads in this forum about how to tweak the camera's picture style and white balance to make camera histograms more usable for "Expose-to-the-Right".
"Standard" is quite contrasty and saturated, what often leads to luminance and/or channel clipping in the RGB output. It worths to try "Faithfull".
Canon uses a different approach in their PowerShot cameras. Instead of Picture Styles they have something comparable, called "My Colors". I wish they would adopt Picture Styles in their RAW-enabled PowerShots at least - and issue Styles for each of those "My Colors".