Muiltiple sites with the same content, our own competitor

We have muiltiple domain names, with web pages that all look different but are powered by the same backend to our e-store. We initally did this to experiment with the look @ feel of each site & have a guinea pig to run test on. After trying out 5 differnt host, we have made the choice of which company we want to go with. But this brings up the problem of subdomains vs. Directories or is it better to just have separate hosting accounts all together? In therory our sites could become their own competitors. Any input?