The circular polarizers are needed because some camera metering systems* are fooled by the light transmitted by linear polarizers.
Your RZ67 (or more accurately, none of it's metering options) is not one of those cameras.
The biggest reason to get a circular polarizer anyways is that it allows you to use the polarizer on any camera that you might have (with the appropriate filter size) without worrying about the issue.
The biggest reasons not to get one are:
a) cost; and
b) if you intend to use polarizers as a Neutral Density filter.
*As an irrelevant aside, does anyone know whether a linear polarizer is compatible with a Canon Pellix?