360s are all external balance because the factory cast iron cranks don't have enough meat to internally balance the piston and rod combo.
The main advantage is it places the counterbalancing weight inside the main caps. That reduces stress and flexing and torsional harmonics in any crank. That adds up to more ability to handle more power, more power out the back, smoothness, better fuel economy, and better life span. Additionally it allows you to use any neutral harmonic dampener and any neutral flex plate and convertor/flywheel.
I internally balance everything I do for those reasons.