I have heard, like most people interested in this period, of the ‘hangar door width’ theory for the reduced wing span of the Stirling. However it was the first of the 4 engine heavies in service, and I suspect that Shorts used the Sunderland wing to save time and money on the Stirling.
Looking at the plan profile of both wings they seem remarkably similar. Later years also showed that Shorts have ‘form’ in this direction, given the bits of Britannia that seemed to become parts of the Belfast.
If anyone knows if this was the case, I would be interested to hear about it.
As for the type of engine. I understand that the Hercules used more fuel than the Merlin, but of course was less subject to battle damage due to no coolant system.