1) Don't use www subdomain if you do not have to. If you or your company has made the mistake of using subdomains for asset management then you likely forced into using www just to be safe.
2) The biggest problem faced by search engines is redundant URIs for the same page. This problem is solved by using a canonical link tag in your HTML. This will perhaps help you more than any other single SEO factor.
3) Make your URIs meaningful. If people can remember URIs well enough to type them out your SEO will be significantly improved.
The most important factors with URIs is easy to remember and the ability to specify uniqueness to the search engine. Nothing else matters with regard to URIs and SEO.