dot or forward slash: does it matter to SE's?

Does a dot or slash help or hender SEO?

[utahclimber]

I've got clients who have either product.clientswebsite.com or clientswebsite.com/product; does one or the other help or hender in SEO?

I've heard that subdomains may be better for SEO, is that so?

Thanks,

Utahclimber