I drove up to Canada last month, eh. The Canadian border guard was much more strict and humorless than the American, but at least she was hot. The US Border Patrol agent was friendly, nice, and barely questioned us.
I live in the Detroit area, where 19 and 20 year olds regularly cross the border because Canada's drinking age is 19. When we went at that age, Windsor also had the bonus of a casino (The Detroit ones didn't exist yet).
Having made the trip probably a hundred times, I concur that the Canadian border guards are much more strict, and lacking in humor. It was very common to have our cars subjected to a random search. If we had a black man in the car, it was guaranteed.
Conversely, the US border guards were so laid back that there were many cases when they didn't ask us ANY questions, and in some cases were busy reading a book and didn't even look at us! It may be worth noting that this was pre- 9/11.