In my impetious youth I bought some expensive spark plugs.......the advertisigng and claims lured me in.  I tried the dual and quadruple electrodes, surface gap plugs, etc.  The end result is that if they were so great for performance and mileage - the factories would use them as part of their expensive research to get better performance and mileage.

There has been a great improvements in plugs when they started making the thin electrodes out of exotic metals - this makes the plugs last a long longer.  The old standard plugs would get rounded off electrodes and that made it harder for the plug to spark properly.

For me.....fancy plugs do very little in a primitive engine like the Suzuki S40.  Get a a factory recommended plug and your engine will run just fine.

I guess the theory is,... better, bigger, spark will give more complete combustion, and that will increase mileage and performance....
... but,... once there is enough spark to ignite the fuel,... any additional spark is redundant...  the explosion is already happening...

It would be like putting a bigger primer on a bullet,... the bullet either fires, or it don't...