Muscle belly length-this is the length of the muscle fibers, not including the attached tendons. If you have greater muscle tissue opposed to your tendon, you may have a greater ability to develop muscle size and strength.
Limb length- Shorter limbs mean shorter levers, and a shorter lever has a biomechanical advantage. The resistance or weight is closer to the joint and is easier to lift than a weight that is further away. In general, if you have shorter limbs, you will be able to lift more weight than individuals with longer limbs, all other factors being equal.