Compelling reasons to install XI when webMethods is available

Hi All,

Has anyone installed XI in an environment where webMethods is already in use as an EAI tool? What reasons did you have to justify the incremental cost of installing and managing XI? We plan to use XI to process messages between R/3 4.6C and external storefront and EDI applications. We already have interfaces to other systems using the corporate EAI shared service which runs webMethods. I'm trying to build a case that bringing in XI now will save us money and am looking for suggestions.

TIA,

Stan