The whole topic of 'who is Canadian' (or insert any other nation) is polarising depending which side of the line you are behind.
If a baby is born in a country - Canada for example - but only lives there for a couple of months the baby is still deemed a citizen of that country.
If he/she then lives in another country for a big part of his/her life, contributing to that society and economy, then he/she decides to move back to Canada, has he/she contributed any more or less than a PR who chose Canada as the country they'd like to live in and has been there for 8 years? Obviously, he/she will have contributed less and it's only by virtue of geography and gestation period that he/she was born in Canada in the first place.
It has to be black and white but the shades of grey come down to what each person gives to the country he or she resides in versus takes from it. There's no measurement for this unfortunately so governments have to create rules, some of which some of the population will rail against.
I was born in the UK and chose to move to Canada in 1997, I became a citizen in 2003. I consider Canada my 'home' country even though I am back in the UK currently (sponsoring my UK partner).
I will be devastated if my partner does not get PR status, for whatever reason the CIC decides - life is not fair - whoever thinks it should be is rather naive. We will fight for us to return to Canada because we will contribute to the country.
So to the question - should a priority be given to citizens versus PR in sponsorship? No it should be given to those who legitimately want to contribute regardless of status.
Jonesy