Platinum vs Irridium spark plugs?

[MagikDraggin]

I changed out the spark plugs today and found that they were Irridium plugs installed by the previous owner.

A local speed pro-shop owner said the platinum plugs are better for my modded LT1 than the Irridiums. So I took his word for it and replaced the Irridium tipped ones with Platinum ones.

What was the idea of the Irridium plugs in the first place? Is there really any discernable advantage of one over the other?

[ErnieN85]

irridum is harder than platnum so it erodes slower. and should last much longer, that said the electrode is much smaller and just might foul easier. I've been told that the are a lot better on the track because of the continuous high rpms usually seen.

[WNH]

The platinum & irridum take longer to wear out.
I think they add nothing more to performance than standard plugs.
That's what I heard, at least.

[jpanek]

The smaller electrode makes a higher electric field near it, requiring less energy to start the spark. I read an SAE paper published by one of the manufacturers, and basically they showed 2 other features I was interested in, higher gas mileage (1-2%) and smoother idle. I didn't notice any difference over the AC ones that were in there before, I just had $100 burning a hole in my pocket that day. I figured if the mileage got better by just 1%, they'd pay for themselves before too long.

Also, since they supposedly last longer, that's less often you have to change out that stupid #8.

[WhalePirot]

My expert (OC Speed) said that the real-world problem is a build-up of a carbon film on the insulator, drawing current from the spark. Every plug will suffer from such. I used to clean plugs, but have not for years.

They use standard Delcos on their race cars.