Increased Muscle Activation in hands. forearms. upper arms and whole upper body meaning bigger muscles and strength gains. 
Less imbalance and injuries by shifting stress off joints and onto the muscles as a thick bar spreads the weight over a larger area of the hand.Forearm extensors and forearm flexors both work equally thus avoiding imbalances. weaknesses and injury.
Unlock muscle gains as these strengthens your hands. fingers and forearms an isolates it such  that your body works on strength and muscle gains in your uppers arms. back and chest.
Natural movement by perfectly replicating natural functions of the human hand – lifting heavy. awkward objects.
Concentration as these are harder to handle and this alone may make you significantly stronger.