Platinum is a much harder metal than copper and has a much higher melting point. This gives platinum the advantage of lasting longer than conventional coper plugs. Besides longevity, platinum plugs in themselves do not make the spark better, or more efficient than copper in any way.
The main advantage of platinum over copper is its ability to heat better, which subsequently burns off deposits better, and its ability to handle high heat, also enables the plug to hold up better and reduce the amount of air gap change over time.
The only way that a platinum plug could be considered any better at creating fuel efficiency for an engine, is if it can reduce the size of the center electrode to the size of a fine wire tip. This reduces the chance of quenching, because it leaves less area for the heat to be reabsorbed by the plug.
His design also gives the added benefit of needing less voltage to jump the gap in order to create a complete burn. This can be an particularly nice benefit for older engines with less efficient ignition systems. Both benefits give the combustion process the potential to create a more complete burn and therefore greater fuel efficiency.