Personally I would not recommend going with a suggestion or working with someone who solely deals in one application/script... because chances are they really don't know anything about programming, only how to modify a script that someone else wrote.
Most REAL programmers who actually do their own programming would never recommend something like Joomla or Wordpress because they would have their own tools and knowledge to build it themselves. The only time they might suggest something like that is because they really don't care about the client, their work, or their portfolio and only want to bang out a "quick and easy" website or store. A real programmer is going to always be up for learning and staying on top of their skill by challenging themselves to bigger and better projects. Wordpress is not that project.
If you really want a pre-made script for a store, then use a script built for a store. Wordpress was built as a blog script, but most people use it for other purposes because that is all they know how to do.