1 domain - 15 sub pages or 15 diff. sites?

[namewaiter]

Hey all,

Just looking for a little feedback, I'm trying to decide on what to do. I have found an area of domains I might register a bunch of or just 1. Obviously they aren't 411 domains or anything, but they aren't that totally bad.

what would be better (this is just an example set of domains)...

(each having there own domain, website)
food4thought.com
cars4thought.com
art4thought.com
domains4thought.com
host4thought.com
subject4thought.com
etc4thought.com

or...

4thought.com
(1 site with simple sub pages for each subject)

I have seen other companies out there doing this type of thing, but what are the advantages to having a whole site for each subject area?

TIA