According to statistics twin helicopters are not that much safer, some of the factors that make you loose an engine have the same impact on single or twin engine, think about fuel starvation for example.
I`m no helicopter pilot but from my observations I have noticed that twin engine helicopters do a lot more risky stuff, while living in Brazil you would hear all the time of accidents involving big twins doing offshore work, while it was rare that some of the smaller city roof hoppers would end up on the news.