So you guys all find the Canadian border personnel to be worse than their American counterparts? I always felt the opposite.
Probably depends on your nationality. Entering a foreign country is a privilege whereas re-entering your own is a right.
I couldn't find straightforward data on the number of border crossings between Canada and the USA. This
source suggests that 18 000 Canadians were denied entry in the USA in 2016 (0.06%). And this
source writes that 30 000 Americans were denied entry. (no percentage given, but probably close to 0.1%)
Looks like the main reason for the difference is that DUI conviction will bar you from entering Canada. The story on this side of the border is that admitting to using cannabis (legal in Canada) will bar you from entering the USA.