What we can say without doubt is that Smith is at the apex of his career. What is remarkable about his game is that in a lot of respects it is utterly unremarkable. He just does what a halfback is supposed to do: get the ball away from the breakdown quickly and cleanly.
So many No9s in today's game are looking to snipe all the time. Smith can do that. He is as quick as they come and keeps defences honest around the fringes. Yet his first instinct is to pass.
A huge reason why New Zealand have been the best team on the planet for the past four years is the speed and quality of the ball they generate at the breakdown.
Smith is the central cog, getting from one ruck to another. He must be the fittest man in rugby to play at that level. It is not just the getting to the breakdowns but the quality of the ball that he delivers. That gives whoever is at first receiver the space and time they need to plot their next move.
On the back foot, his box kicking is sublime. Whether it is a bomb that allows Ben Smith and Julian Savea to contest possession or a kick to relieve pressure, Smith is nearly always on the money.
If Smith is the premier halfback now then that title belonged to Genia at the last World Cup. At times he was close to unplayable. If a defence left a hole open, no matter how small, he would be through it like a rat up a drain pipe.
The problem when your game is based on pace is that you are hostage to the fortune of injuries. Genia's luck did not hold and, after a bad knee injury, he has never quite posed the same threat. That said, he was very polished in the semi-final against Argentina. He is not quite at Smith's level but is in that upper level of scrum-halves.
Carter's best form is also behind him. That is understandable given he is 33 and playing his last match for the All Blacks. I don't know to what extent he is being kept in the team because they feel they owe him the opportunity to play in a World Cup final. He is not attacking the gain line as he used to and, in terms of skill sets, you would place Beauden Barrett ahead of him.
What he does bring, however, is 111 caps' worth of experience, which we saw in the second half of the semi-final against South Africa when he kept the Springboks pinned back in their half with a variety of perfectly judged kicks.
If Carter is the conductor then Foley is the firecracker. I just love watching him. In the framework that the Wallabies have set up, he is given licence to work his magic. You can see his sevens background, the way he takes the ball to the line or changes the point of attack, like he did for that wonderful one-two with Kurtley Beale against England. He has shown flashes of that form in the quarter-final and semi-final, notably with a wonderful miss pass to set up Adam Ashley-Cooper's second try against Argentina.
His bad side rears its head when he sees a kicking tee. Carter kicks the ball serenely through the posts; with Foley it wobbles and wavers. His radar can go on the blink but somehow he tends to make the big kicks, as against Scotland. Hence the nickname: Iceman.
Still, the majority of World Cup finals have been decided by penalties and I would still rather put my trust in Carter.
*Austin Healey is a former England and British and Irish Lions winger.
