The stone cold truth is that butter typically has only two whole ingredients. Cream and salt. Margarine typically has over 15 ingredients with the main one being a vegetable oil of the sort, likely from a genetically modified source such as corn or rapeseed. It is chemically processed whereas butter comes from simply churning cream. With this is mind, why are the heart sensitive apt to buy margarine? That can be blamed on the big food industries and their marketing techniques of course. Butter has been a staple for centuries.
Up until recently it has been demonized. Even though, there is not one decent chef on the planet that will substitute butter for margarine. As a matter of fact, margarine is one molecule away from being plastic. Gross! Sure it takes a special chemical reaction to do this, but the thought of that is a bit disturbing. Another thing about butter, it is almost always sold in sticks, unless it is whipped. With whipped butter the cost is usually more and the quantity is always less because it is less dense. Margarine does come in sticks, but usually it is always packaged in a plastic container, whereas butter typically is not, whipped or in stick form. Therefore, butter takes less of a toll on the environment. Butter can sit out at room temperatures and maintain its form. Margarine will turn into a clear oily mess. Not convinced that butter is better?
Margarine goes through an intense processing system. First, the base which is an oil almost always genetically modified, are steam cleaned which ruins any redeeming nutritional values it began with. They then are mixed with nickel to create a chemical reaction during the hydrogenation process. After the hydrogenation process, which is only partially hydrogenated, the oil turns from a liquid into a solid. After this, the partially hydrogenated product has to be emulsified with cleansers in order to remove the disgusting gray greasy lumps from it. Then it is steam cleaned, deodorized, and bleached in order to get rid of the gray color. Synthetic vitamins, NATURAL colors, and artificial flavors are then added. Interesting that in margarine synthetic coloring is not allowed. Finally the margarine is packaged in plastic, wrapped with a label that has a picture of a beautiful farm on it, and then is marketed as a heart healthy alternative to butter. The process in which margarine is made should be convincing enough that butter is better. To finish, butter is a long time relic of foods and there is no man made substitute for it.