Alloy Prop Shaft and Bearings are Cost Saving Devices, the Stock Plastic Items Wear out rapidly and lets just say Prevention is Better then Cure..

Its Not Nice to replace a Whole Axle because a Bearing has seized and melted it solid..

The Alloy Prop Shaft doesnt Flex and wont snap like the plastic one, it allows more Torque and power to be applied to the wheels so you get the Power down faster