MBWorld.org Forums - SL/R230 Platinum or Iridium? Spark Plugs

The Mercedes owners manual for the 2004 SL500 says to use: Bosch F8DPER, or NGK PFR5R11 which are both Platinum.
For my 2007 SL550 the owners manual says to use Bosch Y7MPP33 or NGK PLKR6A which are Platinum.
I had heard that for the V12 twin turbos you want to use an Iridium plug as Iridium is more durable, according to Clark Rupp, the guy who rebuilds the coilpacks for those engines. HIM, I trust... So for my 2004 SL600, I use NGK Iridium plugs. Otherwise, for all my Benzos I use exactly what the book says to use.
In all my cars I prefer the NGK over the Bosch because my indy says he's come across some broken ceramics on the Bosch plugs.
I learned twenty years ago with my W124 Mercedes cars that substituting plugs is not a good idea, as those cars were very picky about what plug you use. Way back in the early 1980s I had a Chevelle Malibu with a 427 engine that one day just would not start. We tried everything, no start. Finally we got to the plugs which had recently been changed. "They're new, Don't bother checking those."
We did, and the monkey at the parts counter at the local auto parts store had substituted some other plugs. Swap those out with the factory-specified plugs and the car started again! After several weeks! Car-pooling, taking the bus, bumming rides... I was sure happy to have my car running again.
So, plugs do make a difference. They might be the most important part on the car, cause if the fuel doesn't get burned right, it's just a fort with wheels.
If it's not a turbo, there's no reason to substitute Iridiums and Platinums will last just fine. I would change them every 40K miles or less, even though nowadays they are saying "good for 100K miles".