Here ya go, the professional mechanic and racer has found this thread, and will now type his usual spiel about spark plugs!
Nickel tip plugs (OEM type):
Good conductivity (meaning good spark produced), short lifespan, not so durable.
Platinum tip plugs:
Bad conductivity (meaning less spark energy delivered), long lifespan, quite durable.
Iridium tip plugs:
Good conductivity, extremely long lifespan, extremely durable.
You will gain no power whatsoever changing from OEM plugs to iridiums unless at least one of the following conditions is met:
Compression higher then 12:1
Boost higher then 14psi.
RPM higher then ~10,000
High end capacitive discharge ignition system. (MSD doesn't count, 48,000 volts is for suckers, i'm talking the kind that puts out over 100k and will kill your ass if you touch any of the coil terminals. Otherwise known as a racing ignition system)
Other then those situations (almost entirely in pure race or near race motors) you will gain nothing but an indestructable plug.
They do not burn hotter, they do not deliver a stronger spark.
They can, however, survive conditions that murder normal plugs.
My kart engine is an excellent example, it's a single cylinder 100cc two cycle engine that makes [email protected]
That means 14,000 combustions (and sparks) per minute, where a single 4 cycle cylinder at 14,000 is only 7000 combustions/sparks.
A OEM type plug is dead gone destroyed in minutes.
A Palladium (precursor to iridium) plug lasts for a while, but eventually gets eaten.
A platinum plug is a useless power loss that melts just like a palladium or oem type.
A Iridium plug doesn't produce any more power, but it can actually survive not only a race, but an entire season or two.
So, if you don't burn any oil and never want to change spark plugs again, buy iridium.
If you don't mind changing plugs, or your engine burns oil (which will foul ANY plug given time), use nickel plugs that costs $2 each, tops.
A bonus note on spark plug wires:
Anything with a ground strap is useless junk.
Anything with a built in capacitor is useless junk.
NGK, Denso, and Bosch all make good OEM type plug wires, which are the thing to use if you aren't running one of the crazy insane ignition systems.
If you are running one, get the thickest more silicony wires you can.