McIlroy--Winning Battles, Losing Wars

"One Upmanship"
The reason why Adobe InDesign is better than QuarkXPress is very simple—it's more extensible. Adobe has done Quark one better and made it possible for third parties to delve deeper into the core functionality of InDesign than they can into QuarkXPress.

The result is that Adobe will be able to deliver better products at a higher margin and gain a higher market profile and ego boost. No contest. While it's certain to take years to dislodge as successful a competitor as Quark, on this basis alone, Adobe would emerge the winner.