I recommend you stick to Limited RGB unless your TV supports use of Full RGB.
Most TV's expect a signal in the 16-235 range (16 being darkest black, 235 brightest white) which is Limited RGB, all that Full RGB does is remap/stretch this range to 0-255 so it's actually no different to Limited RGB if the TV supports it (it's just mapped differently).
So if your TV is expecting a Limited RGB (16-235) signal and you tell your PS3 to send a Full RGB (0-255) signal, what will be happening is you will be losing all colours in the 0-15 and 236-255 ranges - which is why a lot people notice an increase in contrast, since there's more white and black and less of a gradient.
The most obvious sign that your TV doesn't support Full RGB will be "black crush" which is a loss of detail in darker areas, this is because any colours in the 0-15 range (which should be black and progressively lighter shades of gray) will just be cut off and hence loss of detail.