The league kickers would almost certainly take a greater proportion of their kicks from wide out though because they don't take as many penalty goal attempts which quite often are fairly easy kicks.
It's a hard thing to directly compare because rugby union kickers also turn down possible penalty goal attempts based on difficulty depending on how good the kicker is. Foley for instance almost never has penalty goal attempts from close to the sideline because the Tahs generally kick for the corner if they don't think the penalty goal is close to a sure thing.
I think if did a lot of analysis of goal kickers in league and union you'd come to a conclusion that they are very close in terms of skill level. You'd probably find that the best NRL goal kickers are better than the best Australian rugby goal kickers but probably inferior to the best South African goal kickers.
It's a hard thing to directly compare because rugby union kickers also turn down possible penalty goal attempts based on difficulty depending on how good the kicker is. Foley for instance almost never has penalty goal attempts from close to the sideline because the Tahs generally kick for the corner if they don't think the penalty goal is close to a sure thing.
I think if did a lot of analysis of goal kickers in league and union you'd come to a conclusion that they are very close in terms of skill level. You'd probably find that the best NRL goal kickers are better than the best Australian rugby goal kickers but probably inferior to the best South African goal kickers.