You should care who wins, because if the Canadian leadership becomes more conservative, we can count on their support more. Australia and England may not be as strong allies if they had different leaders.
Look at Spain, we went from strong support from them, to total opposition, because a socilist replaced the guy who was our strong supporter.
I hope Harper wins, his victory will mark yet another defeat for America's political enemies (first Schroeder, and next year Chirac whose approval ratings are in the low 20's).