"Are there any stats regarding NPPL safety verses PPL safety?"
Yes. Can't quote them from memory but I believe only one medical incapacitation with fatal consequences in 8 years since NPPL started.
I have prepared the ones for UK gliding which has operated on the self-declaration basis since 1960s and from 2002 to the NPPL standard including GP endorsement. Guess what - 6 fatal accidents due to medical incapacitation in 36 years of computerised accident records with proper causal analyses (not just 'phase of flight' type analysis). In that time 14.4m flights and probably around 5 million hours. Hence FAR considerably less than the 1% risk accepted by JAA, and no uninvolved third parties affected. One involved third party (student) died in that time as a result of possible instructor incapacitation.
Work out the rate for yourselves!
Oh, and sadly three fatal accidents to tug pilots (also glider pilots) whilst towing, due to medical incapacitation. But they held JAR Class 2 medicals.