Iridium is harder than platinum, and in most cases, iridium spark plugs last about 25 percent longer than comparable platinum spark plugs. ... They won't perform as well as the iridium spark plugs in this case. As the spark ignites the air/fuel mixture, the colder side electrode tends to “quench” the flame.
Benefits of iridium plugs:
1.Improved throttle response
2.Improved economy (though this depends largely on how much you enjoy the improved throttle response!)
3.Increased plug service life (Depending on design, an Iridium plug could last up to ten times the life of a standard plug with little reduction in efficiency over the plug's lifespan)Increased engine power (Don't expect to double your horsepower but a 1 - 3% increase is possible)Improved (reduced) emissions.