Electrically, double, triple, or quadruple electrode spark plugs make no sense.
Electrical arcs will ALWAYS take the path of least resistance. If one ground wire is a 10,000th of an inch closer to the center electrode than the other, the spark will ALWAYS take that shorter path until it builds up more resistance... then the spark will find the next path of least resistance. Thats how electricity works. This is the same reason that Splitfire plugs are a complete joke. In real world operation, especially after setting the gap, you will only have one spark. If you could somehow get the gaps set so that they are absolutely identical.. you MIGHT get two sparks for a very very short time, but from what I know about the voodoo behind electrical behavior, I really seriously doubt it.
The *ONLY* advantages to having more than one ground wire on a spark plug is that once one groudn wire starts to wear down, the spark will then jump from the next closest one. Also, for instance with the Bosch +4 plugs, the spark is not shielded as it is in a standard single wire plug. From what I understand, this will provide a more direct flame propagation in the cylinder.
The best thing you can do for your ignition system is run a higher voltage high-output coil and widen the plug gaps a little, or go with something like an MSD box. That is the only way you are going to honestly get "more" spark.