The only time I really notice a problem with priority bag delivery is at YYZ/YUL for connections to USA. In those cases, baggage delivery is so painfully slow, that priority tags are meaningless.
Just last week, travelling YVR-YYZ-MCO-YYZ-YHZ-YVR, at each station (except MCO) our bags were in the first ten.
That being said, I avoid YYZ, and frequently only have carry-on when I do go there.