I did not fly an Shackletons but Neptuns, a number of friends flew in both and all preferred the Neptune
Neptune’s came to be supplied to the RAF because we had MR Lancaster’s with H2s radar and not much else in Coastal Command and the US said there were not good enough for the cold war,
I flow in the MR Lancaster’s at ST Morgan and operated the H2S radar and also in Neptune’s at RAF Kinloss an RAF Toppclife operating the an/aps20 radar the Americans were right the aps20 was by far better radar .the Neptune was also equipped with additional equipment that the Lancaster lacked, electronic counter measures equipment, sonic equipment, magnetic anomaly detection gear, etc.
The Neptune had crew comfort in mind, sound proofing padding, two bunk beds , a cooker and ash trays if needed