If a site links to you with something like http://www.mydomain.com?var=1234&id=abcd Does that still affect SERP/PR the same as the link beinghttp://www.mydomain.com?
I think having url friendly is better like http:// www .mydomain.com/1234/abcd/ but search engine nowaday can index dynamic url anyway so nobody know the right answer except search engine itself or testing it by yourself.