The short answer
Compare plant milks per 240ml (1 cup), the standard U.S. serving, on four lines: protein, total and added sugars, calcium and vitamin D, and calories. A typical cup delivers roughly 7–9g protein from soy, 2–4g from oat, and about 1g from almond — that spread alone settles most "which is best" arguments before they start.
Protein is the dividing line
Soy drink is the only mainstream plant milk that naturally rivals dairy milk's roughly 8g of protein per cup. Pea-protein drinks match it by formulation. Oat drinks typically provide 2–4g per cup, and almond drinks about 1g — almond beverages are mostly water, which is also why unsweetened versions are so low in calories. Coconut drinks sit near zero. If protein is why you pour milk on cereal or into a smoothie, almond and oat do not do that job no matter what the carton photography implies. If the drink is just a coffee whitener, the protein gap may be irrelevant to you — which is exactly why the use case comes first.
Oat milk's sugar appears in the factory, not the ingredient list
Oat milk is made by enzymatically breaking oat starch into simpler sugars — mostly maltose — during production. The result: an "original" oat drink can show 7g or more of total sugar per cup with 0g of added sugars, because the sweetness was created from the oats rather than poured in. Nothing is mislabeled; the FDA's added-sugars line only counts sugars added as ingredients. But if you compared cartons on the added-sugars line alone, original oat milk would look as unsweetened as unsweetened almond, and it is not. On plant milks, read total sugars and added sugars together — the gap between them is the story.
Fortification is a per-carton fact, not a category fact
Dairy milk's reputation rests partly on calcium and vitamin D. Fortified plant milks match or exceed that: many cartons show around 450mg of calcium per cup (about 35% of the Daily Value) plus added vitamin D and sometimes B12, which matters for fully plant-based diets. Unfortified versions of the same base — common in "simple ingredient" almond and oat drinks — deliver almost none. Two cartons of the same brand can differ on this, so check the calcium and vitamin D %DV on the exact carton you are buying rather than assuming the category covers it.
Barista editions are a different recipe
Barista-formulated oat and almond drinks add oil for foam and steaming stability, which raises fat and calories per cup — often 30–60 calories more than the regular version of the same brand. That is a reasonable trade for better lattes and a poor one for pouring on cereal. "Original," "unsweetened," and "barista" are three different products; compare within one of those lanes, not across them.
Worked example: three cups, one basis
Per 240ml cup: unsweetened soy — 80 calories, 7g protein, 1g total sugar (0g added), 450mg calcium fortified. Original oat — 120 calories, 3g protein, 7g total sugar (0g added, from enzymatic maltose), 350mg calcium fortified. Unsweetened almond — 35 calories, 1g protein, 0g total sugar, 450mg calcium fortified. There is no single winner here: soy leads protein by a wide margin, almond leads on calories and sugar, and oat leads on neither but tastes the richest to many people. If the goal is a low-calorie coffee splash, almond's missing protein costs you nothing. If the goal is replacing dairy in a child's diet, protein and fortification move to the top of the list — a question for your pediatrician, not just the panel.
Sweetened, original, unsweetened: read the lane markers
Naming is not standardized. "Original" usually means sweetened; "unsweetened" is the reliable low-sugar lane; "vanilla" can exist in both. Check the added-sugars line on every carton rather than trusting the word on the front — in this category the same shelf can hold a 0g and a 12g added-sugar version of the same base under the same brand.
Price: compare the half-gallon, not the carton style
Shelf-stable quarts and refrigerated half-gallons coexist, and the refrigerated carton is usually the better value per ounce — with the trade-off that it needs fridge space and a faster finish. Compute price per cup (a half-gallon holds eight 240ml servings) and check whether shelf-stable convenience is worth the premium for your pantry pattern.
What this comparison cannot tell you
Label math cannot tell you which drink your cooking needs, whether you tolerate the gums and oils used for texture, or what suits a medical diet. For soy or nut allergies the allergen statement is decisive. For infants and toddlers, plant drinks are not automatic dairy substitutes — that is a pediatrician conversation. Panel definitions come from the FDA's Nutrition Facts guidance and its added-sugars page; fortification levels change, so recheck cartons after a packaging refresh.
When two cartons are in front of you, AptBite can scan both, line up protein against total and added sugar per cup, and keep the fortification numbers in the same view.
