Different sweet spots on each ball. At the top level the Union ball has a much juicier, rounded shape and corresponding sweet spot. The league ball is a little more pointy and is less forgiving BUT as Braveheart says above, they're generally not kicking from much more than 30 metres, even if it is from the sideline.
Just on the AFL. Has anyone seen the standard of kicking in that competition lately? I wouldn't bank on the answers being there. On the sidelines of my boy's Aussie Rules games on the weekend nearly every week I hear a lot of the parents bemoaning how poorly elite level players kick the ball. There are some kids in the U/13's who do it better and more consistently.
Sure that's not just parents bitching about their team?
There are probably kids that kick more consistently at U13 level
for their age, because they're physically able to dominate and not expend as much energy.
The AFL guys are burning energy and oxygen to a degree that its not surprising they muff the odd kick on the run, and even the set shots where they overthink it.
As @ForceFan says above: its amazing that kicking isn't a major thing taught at the lower level. I coach a bloke who has played rugby all his life, including being a winger for NSW age rep teams, and his kicking style was shit. I sorted it out in about 3 minutes.
So many guys I see in
professional league and union just throw the ball in front of them and hoik their leg at it with all they can muster. Hideous, round-swing action. My Dad, who played country town Aussie Rules footy in South Australia as a younger man, would always laugh at the rugby league players who could barely gain 20 metres on a touch finder.
There is a place for the techniques in AFL to be applied to Union or League, but the difference in ball physics is much more pronounced than between the two. So whatever coach you bring across has to familiarise themselves with the equipment for a long period.
In addition, the situational awareness required for kicking from the hand is different between Aussies Rules and Union, so that has to be taken into account.
That is mostly on the player to hone once the basics of position, foot movement, and purchase on the ball as well as follow-through. Its not difficult to train, and in fact is a lot like place kicking in terms of searching for consistency on a standard touch finder.
But in general play where the pressures are different, you need to practice many more styles of kicking.