Services vs QuereyPath vs Transformations

Hello,

I'm working on a hotel reservation system and was looking for the best choice of existing modules to combine with our custom module.

I wanted to know if you had any wisdom to share on Services vs QuereyPath (or SimpleXML) vs Transformations (or others) for doing the following...

Call external data source with SOAP.
Parse XML response
Convert XML data into CCK fields and/or Taxonomies (some will need to be served in real-time, other can be stored in the database with cron for updating).

It seems that there is a lot of overlap with the above modules and I'm not sure to what extent these tasks can be accomplished with one for more of the above...

http://drupal.org/project/Services
http://drupal.org/project/transformations
http://drupal.org/project/querypath

What module configuration would you recommend? (Or some other module combo)?

Your help would be REALLY appreciated. Choosing the wrong configuration could well sink the project.

Thanks!