Seriously, FIFA ranking as a measure of how good a team is right now, in this tournament?
It's not a really big difference between the three, but I don't think many teams would choose to face Norway among those three. Croatia didn't beat anyone good, the best that Mexico beat was Ecuador, while Norway already won against three teams on that level or better. It's debatable I guess, but that looks harder to me. Unless Argentina fecks up in the quarters, you'll certainly get tougher oppo in the semis.