Boeing versus Airbus is one of the most hard-fought, closely watched marketing battles out there. It's ... one of the most fascinating. Not long ago, it appeared as if Airbus had gained the upper hand. If Boeing succeeds in winning this battle --and it appears to be well on its way--it will amount to one of the great reversals of business fortunes. It will also serve as proof of the wisdom of understanding the marketplace well enough to lead, rather than follow.