I would have thought that if you pick up a body known to be deceased it would be placed either in a body bag and/or strapped to a stretcher. Either way chances are if then found following a subsequent crash of the SAR/medevac aircraft it would be fairly obvious that it wasn't a member of the rescue crew. Therefore the correct call would be the number of people alive on board. If a casualty is picked up who has not been pronounced dead then you would include them in the number on board call, possibly updating that number if the casualty died en route but unlikely as ultimately it would make no difference to the number of bodies/casualties being searched for. The most important thing is to remember that plenty of interested parties scan radio frequencies and patient/casualty confidentiality should be maintained by not giving out any more info than is absolutely necessary over the net.
I would be concerned if a controller determined the number of people on board worthy of rescuing based on a POB v SOB call as both are regularly used to mean the same thing and it tends to be the personal preference of the person making the radio call at the time.
So on the return leg if you report 5 "Persons On Board" we know you have a live casualty, if you report 5 "Souls On Board" we know that the're is a body on board.
That argument falls over if for example you have left a member of your crew at the scene of the rescue, perhaps to help with further casualties, and you are transporting 2 bodies. It would still be 5 "souls on board" but only 3 living!
SW