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I do recall that when I went from work visa to PR, I was asked less questions coming back into Canada. I can't comment about citizenship since while a PR, I became a NEXUS member and don't really speak to anyone anymore when entering Canada using a NEXUS kiosk. I became a citizen while a NEXUS member and noticed no change.
 
It's the "document check" part at the gate (before flight boarding) in several countries in Europe/MiddleEast on the way back to Canada, is the worst. The stupid security questions are mindboggling. They question/check everyone no matter whether citizens, PR, visitors. The security staff/contractors are arrogant and ask pretty invasive questions. It's like they pretend they're immigration officials when they're just private security guards.
Pretty bad when you're flying a North-American airline. Specially the UK is pretty bad.

If possible, try to avoid transit thru europe if you can, and fly direct(non-stop) if possible and avoid transiting thru UK.
 
It's the "document check" part at the gate (before flight boarding) in several countries in Europe/MiddleEast on the way back to Canada, is the worst. The stupid security questions are mindboggling. They question/check everyone no matter whether citizens, PR, visitors. The security staff/contractors are arrogant and ask pretty invasive questions. It's like they pretend they're immigration officials when they're just private security guards.

Yes, exactly! I assume these are all local staff, correct? In other words, not Canadian citizens who have been sent to work abroad. Most of them probably have never even been to Canada. Very ironic for them to grandstand on who can or cannot enter Canada.