ClassiPress is designed specifically for Classified ads listings with a whole range of specific functions to suit this purpose. Vantage is a directory theme, which means it is designed for listings of various businesses, not specifically products at certain prices. Vantage does not have the same functionality as ClassiPress when it comes to catering for price based listings. You can read more about the features of each theme on the relevant theme page:
ClassiPress and
Vantage.
Ultimately what is most suited will depend on your project, but if it helps to get an idea of what others are using each theme for, I'd recommend you browse the
AppThemes customers showcase for a better look at how existing customers are using each, and for what purpose. Thanks.