In terms of the old tart in a new dress, I think the dress on C+ was a major improvement on C, and C++ refined it a little more. I never understood what Sikorsky were trying to achieve with the D, particularly if pitching it to offshore customers. More power is always good, but does the fancy avionics package in D get you around the patch any faster or safer than C++? Just trying to understand why an operator might decide to upgrade a C++ fleet to D, particularly with AW139 being an alternative in the market.
Esso Australia have just upgraded from six S76C to four AW139. Which is an upgrade equation I can understand. And the Macau operation changed from S76C+ to AW139, I can understand that also. But if C++ is your starting point I don't understand why you might want to change those for a D.