Margarine was banned until Newfoundland joined Canada which always used margarine and was a big producer of it. It was outlawed in Canada because the dairy council had a lot of weight (and still do) in politics. It was not that long ago that the church and the dairy council were the most influential organizations in the country...actually...have things really changed?
Butter tastes way better but it is also high in saturated fat. While margarine is more chemical it is usually vegetable oil based and healthier...but that is a big debate.