It’s not as nuanced as it sounds, I promise.

The composition of butter and margarine, specifically their fat content, affects the texture and–to a degree–the flavor of whatever it is you’re baking. And while it’s mostly preference-based for whichever you choose to use, it’s helpful to keep in mind how either impact may impact what it is you’re baking; the type of butter can affect the overall consistency of the baked good if the other ingredients involved have tendencies to reduce or induce moisture. But, as a disclaimer, I am incredibly biased towards sweet cream butter and will always choose it before the Butter That’s Not.

 
Having done some research to explain my experience through more technical terms (and with proof), blogger Kelli Foster on her blog The Kitchn has this wonderful post on the differences between butter and its knockoff. Typically, margarine isn’t made from milk or dairy products; vegetable oil supplies its fat, and other ingredients are combined to help it mimic butter in both consistency and flavor. And, remembering a few fragmented details about the types of fat the body processes, there are the plant-based/healthier fats known as unsaturated fats, and animal byproduct-based fats/unhealthier fats known as saturated fats. And don’t let the oxymoron confuse you, margarine is still a fat and can be harmful in copious amounts, but calorie wise you might save anywhere from 20 to 100 depending on the brand and the ingredients.

 
But this isn’t about health.

 
Despite the heavily water-based components of the Not Butter, I’ve found that it actually reduces moisture when used in baking. That being said, it’s not the best bet if you like mushier and less compact desserts. HOWEVER, if you like cookies that skirt the fine line between crispy and burnt, then this pseudo-butter is for you! The dough flattens and spreads for a crunchier cookie because the moisture (mostly water based) evaporates more evenly during the baking process. Other good, non-moist desserts that would benefit from this include scones for their crumbly texture, biscotti for their teeth-shattering texture, and biscuits for their flaky texture. So, in conclusion, there is at least some merit to the self-proclaimed Butter That’s Not anamoly.

 
Now my first love, sweet cream butter, differs from its doppelganger for its obvious basis of dairy products and saturated fats, naturally having a lower water content. It retains moisture much better when baked, as well as infusing an unmistakable creaminess that is lost with margarine substitution. Sure, the calories per serving are heartstopping (literally), but my cholesterol can meet me in hell for it because, again, this isn’t about health.

 
If you want cookies that hold their form, come out chewy, and taste buttery and delicious, then don’t ever settle for This Shit Sure Ain’t Butter. The real deal seals moisture and assures a dense, cakey consistency for whatever you put it in. Use it in breads, cakes of all kinds, muffins, puff-pastries, brownies– anything you want to taste good.

Of course, this is all speculation and preference, and my mother (a.k.a. the superior baker in every way to me) defends margarine with her heart and soul, so don’t be afraid to experiment with different leaveners to find the consistency that you crave in your baking.
And when you come to find that there is no better substitute for butter than itself, don’t be afraid to come crawling back.
Just kidding (mostly).