Um...Blogbytes, why do you presume I even know rugby???
And since they brought in spot kicks, the aim is to keep it low and hard, into the corner of the net. If you have watched any World Cup, EURO or any other major competition that could result in penalty kicks you will notice the same trend for penalty kicks. Keep it low, hard and in the corner. Yes going into the higher half of the goal can be more successful, but its way more risky, too risky to rely on it in the most pressure filled position possible!!
A well placed penalty kick, low and in the corner, will only get saved if the keeper guesses the right way. But do you want to be the idiot who blasts high and left when the keeper went right???
Go and watch some football mate!!