
Years ago when I was a food editor I really did a lot of testing of recipes. The conclusion was irrefutable: when it comes to baking, nothing touches the results of high-quality butter.
I also had my doubts then about margarine, as it is a highly processed product. Some years later my worries about magarine as so-called "healthful" was borne out by medical studies: it's bad for us and contains trans-fatty acids, etc.
Okay,

yes, they've improved it with spreadable margarines since.
But for baking you have to use hard margarine, as the spreadables contain too much water. My argument is this: butter is normally (from reputable sources) a totally natural product which has been used for centuries. As long as one doesn't overdo it, butter won't harm anyone who eats a healthy diet.
Use BUTTER!
Oh, by the way, here in South Africa as no doubt also in the USA we get perfectly nice butter-plus-sunflower oil spreads, which is preferable to pure butter when it comes to spreadability in cold weather. Also nice for a blob on cooked veggies. (This is just by-the-way chat!

)