***.mydomain.com OR mydomain.com/*** Which is best for SEO

[nicheminer]

I have a bunch of related products to market and I have a basic website for each of them.

Started a while ago with product 1 using product1.mydomain.com

I have a Squidoo lens and hubpage driving traffic to this sales page.

Now I'm gearing up to start adding other websites for the new products, but don't know if there is any advantage in how I set up the url.

At the moment the 'holding' domain (mydomain.com) is just that - there is nothing on it other than the current sub domain.

Would it be better from an SEO point of view to use the main domain as an overall pre-sales site with links to all the products in folders rather than sub domains?

I'm thinking that one master url with folders might be more of an authority type site.

I intend to build an SEO backbone for links, so want to get the initial setup correct.

All traffic will be organic using semantic related keywords. No PPC.

Have you any preference from your own experience as to which way will give the more profitable route in the medium term.

Graham