You need to understand your body and how different clothes will affect you upon wearing them. If you wear very tight running shorts, blood and air circulation in your blood will be greatly affected. If that happens, your speed will be greatly affected, which will cause more running time. If your body is relatively thin, you should not wear oversize shorts because they will likely inconvenience you while you run. You will need to find running shorts that fit you comfortably to allow easier and effective movement of your legs.
You need to also consider your style of running. Since heavy shorts will be burdensome for marathon runners, it is only important if they wear short and light shorts which will be more comfortable to them. However, if you are a short-distance runner, you can comfortably clad in heavier running shorts provided they fit into you well. If, for instance, you are participating in a steeplechase competition, you will need to wear light and short running shorts which will allow you make the jumps effectively, and with a lesser strain. This is due to the kind of stretching your legs will need to do while making the jumps, which may be affected by the kind of running shorts you are wearing.
Finally, you need to establish the purpose why you are running. If you are participating in a training session. Then you can use heavy running shorts even if you want to train for a marathon. In fact you need to train with heavy running shorts to assist in making you more resilient. However, if you are participating in a competitive race, you need to ensure that you use the standard recommended running shorts. If you are participating in exercises or training sessions that are too physical, you need to have running shorts, preferably cotton shorts, which can absorb the sweat, hence helping you remain comfortable.