best for spark transfer; dull or sharp edges?

RustyRatRod said

Can you post your information source on that? I've always read that copper conducts better. As a better conductor, it would seem that it would take less voltage to fire, right? The only benefit I'm aware of with platinum, iridium or any other "exotic" metal is that they simply last longer.

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I’ve run Denso iridium plugs, some NGK iridium on a few motorcycles, most noticeable differences were on a 79 Triumph Bonneville 750. It started (kickstart) easier, had a more consistent/steady idle, was able to try lowering the idle speed below the ideal (just to see) and it had crisper throttle response when cracking the throttle. Slightly more responsive. That was all I saw, easier starting, strong idle and snappier throttle response. Couldn’t discern anything else when riding it, accelerating etc.
From my research at the time it was due to the thin center electrode design, not due to a metal. That it was a iridium only allowed longer life using such a small diameter electrode.