An extended tip plug is often advantageous because it moves the ignition source point away from the wall of the combustion chamber and out into the center of the chamber where it will be more likely to burn faster due to increased charge motion and a more centralized source of ignition. This can mean a more efficient engine because the peak cylinder pressure point will occur sooner, at a time that is better for producung more torque on the crank pin. Also, less negative work will be done in the compression phase since timing may now be retarded.
Here are some extended tip plugs:
