A pure sine wave signal will peak about 3dB lower on a VU meter (RMS) than on a PPM meter (peak). A more complex signal which involves transients such as music will produce a larger difference. How much larger depends on the crest-factor of the signal, which is a measure of how "peaky" it is. Peak values can end up 10-20dB higher than VU values.
When recording amplified music which is louder than the applause from an audience position, that difference is likely to range around 10-12dB. When recording on-stage near transient rich acoustic sources (say drums and percussion) which have not been reamplified and limited through the PA, the difference can be significantly larger, say up to 20dB.
I updated firmware back in December when I picked up a second PR2 but have yet to seriously looked into the metering.