Two of everything for the obvious reasons is what is best.
Only people who don't think so are the people not flying and that have to justify to other morrons why pay for a more expensive machine when a cheaper one can to their knowledge do the job. Why pay for two guys when you only need one to move the stick... Thats how too many customers think and sometimes some operators too... unfortunatly.
Look at the safety records of twins vs singles in EMS work and single or dual pilots in those two types of machines... let the numbers speak for themself.
I know that a lot of other factors have to be taken into considerations (weather limits, crew duty/rest time, etc...) but there is no doubt in my mind that two of each is better than one.
Been there, done that...