There does seem to be a general reluctance, from the newest tyro SPL to the wizened old ATPL to use the M and P words.
You hear people saying that they "wish to declare an emergency" or "We require a priority landing" or "we are temporarily uncertain of our position" or "we have a problem up here" or "we are a little low on fuel."
"Mayday" and "Pan Pan" are there to communicate rapidly with ATC that you require their urgent and full attention and that your circumstances place you in greater need of a service than others on frequency or in the area.
If you judge that those circumstances apply you should use the appropriate word, and not faff about trying to sound like a cool Apollo 13 jock or whatever.
As a frinstance, I was flying my Aztec at night in broken IMC when a series of things went wrong with the electrics, one after the other - various circuit breakers popped, but reset OK, one NAV radio failed. None of these things really compromised the flight per se, but I was thinking "there's something awry here, and I really don't want to be up here, in controlled airspace, at night, in IMC with a total electrical failure" So I declared a PAN PAN, was instantly instructed to go speechless, to preserve battery, and was swiftly handed from one guy to the next to a landing at Biggin, all beautifully co-ordinated such that I never had to say a word (though I was given the opportunity to change squawk to indicate lack of willingness to comply with an instruction.)
It was like well-oiled clockwork...extraordinarily professionally handled and, like Flower says, why these guys are so well trained, highly paid and underworked
So use the magic words and get fantastically well looked after.
W