manfromuncle
Having flown singles and twins extensively I have no doubt that for most business flying, twins both are safer, and importantly, feel safer for pilot and pax. Apart from anything else, you do have to give some credence to the views of the world's regulatory bodies.
Accident stats need to be viewed carefully to compare apples with apples. Don't forget many twins are actually used in more hazardous operations - especially night and IMC.
No question pilot error still heads the accident cause list, but when you consider the small number of mechanical failures that do occur, engine failure is quite significant. As Bravo 73 says, twins (esp IFR) come with a lot more redundancy than singles, apart from the engine.
When I'm flying at night, in IMC, over water and making congested/confined area approaches that second engine provides me - and my pax - with a lot more confidence. With justification.