I wonder about platinum plugs. Those plasma plugs (uh, where’s the freakin’ URL, I saved it... oh well) from Pulstar (something like that) don’t appear to be that much off a boost (although there is a small one, according to sparkplugs.com ), and platinum plugs give even more.
The short answer is that there is no detectable difference on the dyno.
The long answer is that the flame front propagation speed is pretty fixed. It is kind of like the difference between starting a gasoline soaked bonfire with a match or a lighter with a 2 inch flame.
A bigger broader spark may act like slightly advancing the timing, which does improve performance, but like I said we couldn't measure the difference. I suspect that simply replacing old worn out plugs improves performance : )