When I bought the bike, the man in the gas gas shop, recommended standard plugs over iridium for the bike. I run iridium on pretty much every bike I've ever owned. As the people on here have real experience, what do you run?
I personally go with the S, its cheaper than the rest with no noticable difference that I can find. Some people have found the iridium plug helps to clean up the jetting/burbles a bit. I can buy 3 x the BR8ES for the same price as 1 x BR8EIX