What possible logical justification can anyone make for not making a Mayday all?
Let me offer another angle.
Two distinct priorities of emergency exist for a reason. If two aircraft have emergencies at the same time, the prioritisation may be necessary. As someone who has spent a long time flying behind one engine by design, if I were able to fly satisfactorily with one engine out in a twin, I'd be uncomfortable about competing for ATS resource against an aircraft where immediate ATS assistance could really make a difference to life or death. That is the potential "cost".
If, as would usually be the case, I am the only aircraft with an emergency at the time, why does it matter whether I declare a Mayday or a Pan? ATC will devote itself to helping me regardless of the status I choose.
If you have to think about whether declaring an emergency is necessary, the decision is already made for you, just do it!
That is naive. Wherever you choose to set your threshold for asking for extra help, there are always cases at the margin. If you can honestly say that you've never
thought about declaring an emergency and decided not to do so, you clearly don't do enough
thinking when you fly...
