The iridium are generally a harder wearing plug .. they also tend not to foul as easily . But that’s never a problem I’ve found on these bikes . . I used to use them on my tl1000 which is meant to be hard on plugs .. but have switched back to standard type plugs .. I’ve not had any starting or fouling issues . . Maybe the bosh silver plugs could be a better choice ?
I think the different heat rating could be because of the Aussie temp .. lucky buggers .. : )