I am truly amazed that we are having this conversation. The UK CAA and JAR-OPS 3 make it a requirement for twin engined helicopters for Offshore Public Transport. More meaningfully, US owned Oil Companies also make twins a requirement, along with rebreathers, survival suits and personal PLBs. Strange they don't make it a requirement in the US. From this it can be deduced that these august bodies consider twins to be safer.
Unfortunately standards within UK operators, owned by North American companies are not as high as they have been in the past. Maximum return on assets is all that matters. It will all end in tears.