Based on the brief description you have given of your project, at this time I would personally say that the
ClassiPress theme may be better suited to it in relation to the functionality that it already has. That is, you can create custom forms for ad listings, and search based on those custom fields. The advanced search in ClassiPress can be seen on the
demo site as "Refine results" in the sidebar, and those fields which are used in the advanced search box are determined by what you set up. Vantage does also include a custom forms and fields functionality, however at this time you cannot search by those custom fields (although this is planned for a future release of the theme). Of note, neither Vantage or ClassiPress includes eCommerce functionality which would allow a customer to purchase an item directly through the site. Both themes allow you to create as many categories/subcategories you require.
Ultimately both themes are capable of what you describe in the sense that there is no encryption which would prevent you from making the relevant changes required for your purposes. It comes down to which of these would require the least amount of customization in order to suit your project. Thanks.
