A rug is bought for how it looks and is lived with for how it wears, and the two are connected mainly through the fibre. Each of the common fibres has a characteristic way of giving up, and once you know what it is, choosing for a particular room becomes straightforward.
Wool is the default for good reason. The fibre is naturally springy, so a wool pile recovers from being stood on, which is why a wool rug in a hallway still looks like a rug after several years while many others look like a path. It takes dye deeply and ages by softening rather than by going shabby. Its drawbacks are real but manageable: a new wool rug sheds loose fibre for several weeks, it should not be left damp, and it is the most expensive of the common options. In any room where people walk a lot and the rug is meant to last, wool repays the difference.
Cotton is the opposite proposition. It is soft, inexpensive, usually flat rather than piled, and frequently washable, which makes it the sensible choice in a room where spills are expected and a rug may need to go into a machine. What it does not have is resilience. Cotton crushes underfoot and stays crushed, and it fades in direct sun faster than wool. Treat a cotton rug as a five-year item that can be replaced without regret and it is excellent value; expect it to be an heirloom and it will disappoint.
Jute, sisal and the other plant fibres are chosen for texture, and they bring a great deal of it. They are tough underfoot, they are usually the cheapest way to cover a large floor area, and their coarse weave adds a surface that a room full of smooth things badly needs. The catch is liquid. These fibres absorb readily and mark permanently, and they cannot be cleaned aggressively without damaging the weave. They belong in rooms where nothing is eaten or drunk, and they are a poor idea under a dining table however good they look there.
Synthetic fibres have improved and should not be dismissed, particularly for rooms with small children or animals. They clean easily, resist stains, do not fade much and cost little. Their failure mode is permanent flattening: a synthetic pile that has been walked on in the same line for two years will keep that line, because the fibre has no memory to recover with. They are best where the traffic is diffuse rather than channelled.
Construction matters alongside fibre. A hand-knotted rug wears from the top down and can look good for decades; a tufted rug is pile glued to a backing, and when the glue eventually fails the rug sheds and cannot be repaired economically. A flatweave has no pile at all, so it cannot crush, wears very evenly and is easy to lift and shake, though it is less comfortable and slides more readily.
Two habits extend the life of any of them. Use a pad underneath, which stops the rug moving, lifts it slightly off the floor so grit falls through instead of grinding, and adds noticeably to the comfort. And turn the rug end for end once or twice a year, so that the traffic lane and the sunlit stripe do not spend their whole life in the same place. Neither takes long and both are worth more than any amount of careful shopping.