Originally Posted by Davejam
There is a difference according to NGK.
https://ngksparkplugs.com/en/resources/iridium-ix-vs-oe-iridium-spark-plugs
Additionally seems like OE have higher copper core for improved heat transfer versus nickel core in IX.
So, there is a difference...whether that is worth the $ is up to you.
Correct. The difference is not in performance but in lifespan.
In your link, NGK states:
Originally Posted by NGK
These two plugs perform similarly, due to their fine-wire tip design, but the service interval is different; the Laser Series are typically designed to last 80 to 100 thousand miles, where as the Iridium IX® spark plugs are designed to last 40 to 50 thousand miles.
And the same can be said for Ruthenium as well. No increase in performance but super extended life.
Likely the choice for transverse V6's with difficult to reach rear banks, just like the OP has opted for.
But if you're servicing a 4-banger it becomes a matter of preference in easy to perform service intervals only.