Flew 139 for years, with tight economics they fell back out of favour and it was back to a 76 C+, C++, B. Preferred the updated avionics of the 76 to the high alt jet Honeywell in the 139. But that was for non-SAR work. 76 was aimed at the corporate market, industry used it for everything else 'cause it was cheap and survived relatively well in remote environments. Some pilots I flew with wouldn't shut down the 139 anywhere there wasn't a battery cart, the 76 didn't know what a battery cart was.
Never flew the D but it still seemed stuck on the US eastern seaboard corporate world without the utility of either the C++ or the 139.