"The JetRanger’s history of reliability and flexibility, combined with the best safety record among all single-engine aircraft"
From
BHT webpage.
I have heard this and read for many years. I remember reading a booklet from the NTSB about single engine aircraft accident statistics where where it was clear that the B 206 was safer than other single engine aircraft. You could try to search
www.ntsb.gov also!
It is amazing if this still holds true with all the single engine turboprops on the market like Cessna Caravan, Malibu Mirage, TBM 700 & PC 12 that a helicopter would be safer considering the much more dangerous nature of work that a helicopter will perform.
I remember though reading somewhere that Cessna claims that the PT6 in their C-208 has the best reliabilty record for an engine.