At a previous employer, it was a pan but a crew incapacitation was a mayday... never understood the logic.
I'm of the school of thought that you can never know for certain why an engine just quit so why risk a pan call? (Recall BA038 and the way in which both donkeys died within a few minutes/seconds of each other). Make it a mayday but manage the situation and fly the plane like you made a pan call if that, practically speaking, is the better or safer thing to do.
An old CRM instructor told me he had a dear friend who declared a pan for a guy who reporting breathing difficulties. Prior to landing, the guy died of a heart attack. Victim's family tried to sue the airline / skipper for not declaring a mayday, claiming the few minutes saved would've made all the difference (absolute rubbish, obviously). Moral of the story, in this stupidly litigious world, don't settle for second best.
Controversial point of view? maybe.