The two cuts come from muscles that work differently and behave very differently in the kitchen. Breast meat is lean and has fine fibers; it cooks quickly, but the window for doneness is narrow, and a delay of a few minutes can dry it out. Thigh meat is fattier and contains more connective tissue; it cooks more slowly but tolerates longer cooking and rarely dries out. The choice depends on how long the dish takes and how much attention you can give it.
The breast is a little-used muscle in the animal, so it is low in fat, has fine fibers, and is light in color. It cooks quickly and has a neutral flavor, allowing spices and sauces to stand out. Its main challenge is the narrow window for doneness: there are only a few °C between the target of 74°C / 165°F and the point at which the meat begins to dry out. Without a thermometer, it is difficult to hit that window, and the most common mistake is overcooking the meat in an effort to be safe. For this reason, the breast is not the cut to cook last in a recipe; it is the one that needs the closest attention.
The thigh is a muscle the animal uses constantly. It contains more fat, more connective tissue, and more of the pigment that darkens the meat. During long cooking, connective tissue melts and turns to gelatin, so thigh meat does not have to stop at 74°C / 165°F; it can remain juicy even at a higher temperature. In fact, its texture improves at around 80°C / 175°F. It has a more pronounced flavor and is satisfying on its own. It generally costs less than breast meat, which is another advantage in many kitchens.
The choice depends on the dish. Schnitzel, grilling, salads, and quick stir-fries call for breast; those dishes use thin cuts and are finished in minutes. Stews, long oven cooking, casseroles, tandoor-style roasts, and serving a crowd at a barbecue call for thigh. Thigh is also preferred for ground chicken because ground breast turns out dry and crumbly. When roasting a whole chicken, both cuts are on the same tray, which directly creates an even-cooking challenge. Bone-in and boneless thighs also differ: bone-in thighs take longer to cook but have more flavor.
If the two cuts are cooked at the same time, their different cooking times need to be managed. Although the breast is thicker, it reaches its target sooner; in a whole chicken, the breast finishes first and dries out while it waits. To address this, start cooking the chicken breast-side down or cover the breast with foil while leaving the thigh uncovered. If cooking separate pieces, put the breast on the tray later. Insert the thermometer into the thickest part of both pieces without touching the bone.
There is no meaningful difference between the two cuts in storage: keep them in a sealed container on the lowest shelf of the refrigerator, and do not thaw them on the counter. After freezing and thawing, thigh meat releases less water than breast meat because its fat and connective tissue retain moisture; this is another reason to choose thigh for meat that will spend a long time in the freezer. Both cuts have the same doneness measure: 74°C / 165°F. Do not leave cooked chicken at room temperature for more than 2 hours; in hot weather, reduce that time to 1 hour.