I think the key thing is that it depends when the number 2 is making centuries. Using the Marcus North example, if he's coming in at 4/300 and then piling on the runs even more, I'd definitely take the number 1 batsman. But if he's coming in under the pump at 4/120 and reeling off a century, then it's a different story. The thing is though, it's centuries that win you games, not 50s. A 50 will help set up the win, but the century is what you need; I daresay that's what Australia's been lacking recently, with too many players making the start, but getting out between around 30-60, with no one really kicking on.
Welcome to the forum btw Stoggler