Whether you should use RGB Full or RGB Limited is not decided by the media you are playing (games, DVD, Blu-ray) but is instead related to the HDMI input on your display (and how it is calibrated).
RGB Full has black at 0 and peak white at 255. (This is sometimes known as PC levels)
RGB Limited has black 16 and peak white at 235. (This is sometimes known as video levels - and is the broadcast and production video standard used in both SD and HD video standard 601 and 709)
If you replay a Blu-ray or DVD (which will be encoded 16-235) in RGB Full, then your PS3 will remap the 16-235 video to 0-255, which has the side effect of clipping any <16 or >235 content that may be present on the Blu-ray or DVD (sometimes known as Blacker than Black - BTB - and WTW - Whiter than White) (*)
If your display is a regular HDMI TV, then it is almost certainly delivered configured and calibrated for RGB Limited - as this is what an HDMI DVD player, HD satellite receiver etc. will usually output by default if using RGB output. (As 16-235 is the video standard used for DVD, Blu-ray and TV broadcasts).
If you are feeding your device to a PC monitor - configured for 0-255 levels (which is what most DVI PC monitors are set-up for) then RGB Full would be the best choice.
If you feed a 0-255 signal (RGB Full) into a display configured for 16-235 (RGB Limited) then you will get crushed blacks and clipped whites (as the content below 16 and above 235 will not appear any different to content at 16 or 235) - and the image will also appear to be artificially more saturated (richer colours)
If you feed a 16-235 signal (RGB Limited) into a display configured for 0-255(RGB Full) then you will get grey-ish/milky blacks, dull whites - and the image will look washed out and de-saturated (less colourful) (As the 16 black level in the source will be displayed as grey as it is above the 0 black level of the display, and the 235 peak white of the source will not reach the 255 peak white of the display)
(*) BTB and WTW in 16-235 video shouldn't contain picture content on properly mastered material - but they should ideally be preserved to allow overshoot and undershoot on sharp transitions (particularly in analogue sourced content) to be preserved without clipping to avoid ringing.