Iridium last longer than platinum IF THE CENTER ELECTRODE HAS THE SAME DIAMETER. If the iridium is made with finer electrode (like the Iridium IX) than the platinum, it wouldn't always last longer.
http://www.ngksparkplugs.com/pdf/DYK_LaserIridium_vs_Iridium IX.pdf
As said here, Iridium IX last approximately 40-50k, half of the 80-100k for Laser Iridium.
http://www.ngksparkplugs.com/pdf/DYK_LaserIridium_vs_Iridium IX.pdf
As said here, Iridium IX last approximately 40-50k, half of the 80-100k for Laser Iridium.