Comparing ESB and SOA seems more like comparing a road and a car. An ESB is more like the medium upon which an SOA can be implemented. (It's not the only medium, of course.) I understand the horizontal versus vertical slices you describe on the Computerworld article, however, I still feel that an ESB is a thing you can buy whereas an SOA is more of an architectural methodology - not something that sits on a shelf.
The Message Oriented Architecture could be more analagous to an SOA. Both could be implemented utilizing an ESB, however, differently. Care to compare and contrast MOA versus SOA?
Yes, ESB paves the road and SOA guides the traffic. There's not like 'windows vs. unix' case.
But it's good approach to present the horizontal versus vertical slice view to the business to buy SOA idea. That is the value from the article.