Single engine vs. multiengine, I'll go with the latter anytime. Statistically though, the majority of EMS accidents (in the USA at least) stems from a lack of cockpit crew training and safety culture.
SAS, while I am with you for the full IFR suite and two ponies under the hood (I fly where you have flown before), I think that two pilots in the cockpit are not an affordable reality, at least in the USA and unless some Program Director feels like forking out the extra "dinero". Adequate (read rigorous) training in both flight and CRM specialties shall have to be entertained by the operators here.
The FAA has just released an Advisory Circular to establish minimum guidelines for Air Medical Resource Management training.
It shall be interesting to see how the cockpit crew proper is going to have to interact with the "cabin crew" for the greater good.
http://www.airweb.faa.gov/Regulatory...LE/AC00-64.pdf