4 to go  

From what I have seen:

Dual pilot can work either way.  In aviation overall, (as in not just helicopters,) the smart companies hire guys with tons of experience as PICs, assign SICs who would benefit from their experience, and the PICs let the SICs do the stuff needed for the SICs log book when it is within company policy so that the SIC can qualify as PIC.  When the SICs make PIC, they will get the big raise and their SICs will be senior SICs on the verge of PIC, and their flights will be scrutinzed by the powers-that-be much more than the usual experienced PIC flights.

Some really senior guys will want to be hired and work as SIC as a retirement job, so they don't have the responsibility and possible stress of being PIC.  In cases where there are two PIC qualified pilots assigned, usually the senior is assigned as PIC, although the crew may negotiate where the coin-toss loser has to be PIC during daylight west-bound flights and SIC during east-bound flights in fixed wing, and vice-versa in rotor wing.

Like I said, it is what I have seen, and I could have greatly misinterpreted things.

I hope this helps.