Difference between Laser Iridium vs Iridium Spark plugs?

[ms2000]

Dealer said
NGK Laser Iridium Plug Number LTR5BI-13 Spark Plug - 90083

NGK site lists several starting from: NGK Laser Iridium Plug Number LTR5BI-13 Spark Plug - 90083
100k lifespan as per NGK

Then there is
NGK Iridium IX Plug Number LTR5IX-11 Spark Plug - 4344
50k lifespan as per NGK

One is about $19 and the latter is about $11.

Anyone can share there experience? Also with Laser Iridium Plugs, how often or what mileage do you change them?

em, Rock Auto shows different gap between the two above. But NGK web site shows identical gap, 0.052. But when I click compare, it says 0.050 and 0.043! What is going on?

 

[MarioT]

IIRC, Laser Iridium also has a platinum "pad" on the ground electrode for longer lifespan.
IX only has the Iridium tip & std nickel ground.