What’s the best spark plug replacement for my Generac GP6700E generator?

[Japanese]

I'll stick with the theory of longer plug life. 100k miles versus 30k miles between plug changes.

Iridum spark plug longevity
https://ngksparkplugs.com/en/resources/iridium-ix-vs-oe-iridium-spark-plugs

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.