Willie and Clunck
I have always thought "Mayday" and "Pan" to be more appropriate because it conveys the seriousness of a situation. We often get a pilot telling us they have some problem (control, electrical)..and we have to ask "do you wish to declare an emergency?"
As a side note...what do you think of the term "fuel emergency". To my understanding it was only brought in because pilots used to say they were low on fuel to try and get short cuts or a quicker approach. In ATC an aircraft will only get priority in a fuel situation if they declare a fuel emergency.