...This makes more work when creating hyperlinks from one section to another because you may need to use a full url instead of a simple relative link. I believe you'll find it easier to use folders.
Yes, definitely additional administrative issues come with subdomains. They're a piece of cake to set up in Lunar Pages CP, but managing separate sites can be a hassle.
Subdomains are a really good feature when you want to isolate software applications, like forums or e-commerce systems. Keeping that code isolated in a subdomain and using a separate database helps you manage software more easily and with less risk of an error crashing an entire website.
And someone correct me if I'm wrong, but as of a couple of years ago using subdomains was really beneficial in search engine marketing. SE's considered (and certainly still do to some degree) a subdomain as a completely new and separate web site. Just make sure there's enough content there to justify it.
If you're going to use it for separating content as you suggested, and not for a specific software system, I'd start with the easier domain.com/cars, and if you develop enough content there to justify using a subdomain, turn that folder into a subdomain and use 301 redirects to point inbound traffic from the domain.com/cars location to the to cars.domain.com location.
Jerry
