Think of the final dish first. A shape should make the food easy to eat and stay pleasant through its intended cooking route.
Long and slenderFor bowls and twirling
Long strands suit dishes where a fork, chopsticks, or spoon can gather a portion. They work with clear broths and many smooth sauces. A light toss after draining helps prevent sticking; a little reserved cooking water can loosen a sauce if appropriate.
Long noodles can become awkward in a spoon-based soup if left uncut or bundled too tightly. For soup, choose a length and thickness that are manageable in the bowl.
Flat and ribbonedFor broad coverage
Flat noodles offer more surface for sauce and a substantial bite. They suit stir-fries and brothy dishes where the noodle should remain noticeable. Watch thickness: a wide noodle may take longer to cook through than a narrow strand.
Short and sturdyFor scooping and baking
Short forms work well with chunky sauces, vegetables, and ingredients that are picked up together. Sturdy shapes are practical in baked dishes because they need to remain intact after mixing and heating again.
Thin and delicateFor quick finishes
Thin noodles often cook quickly and can soften fast in hot broth or a pan. Check them early, and consider cooking separately when their starch could cloud or thicken the soup more than you want.