Multiple Domains or Multiple Directories?

best structure for search engine placement?

[jpweb]

I am about to set out on a new project, and I wanted to ask for the advice of this board on which direction I should go.
I am building a new website for my target audience, and I was wondering what the most beneficial website structure would be in terms of search engine placement, while still providing the best user experience.

I have the following domain names:
fruit-widget.com
apple-widget.com
orange-widget.com
banana-widget.com
kiwi-widget.com
grape-widget.com

I am wondering if I should develop fruit-widget.com, and then just make new directories for each of the other specific areas. (Ex. fruit-widget.com/apple)

The other natural alternative is to just link from fruit-widget.com to the other members of the network.

Which design makes the most sense?

[tedster]

Unless each subtopic is huge (thousands of pages worth of real content) I'd say you want one domain.