The two main benefits are a stronger spark is delivered and you don't get voltage loss like you would with a dizzy, as the powered is delivered straight to where it's needed, i.e. the plugs.

You then don't get the chronic misfiring, nor need to run tiny plug gaps, which otherwise would be needed on higher power Cosworth's.

The dizzy IS still required for the phase sensor and also it can't simply be removed as it's part of the oil pump drive, so this needs machining work etc it can be removed and the sensor needs moving to the cam cover.

Martin