The diversity of your inbound profile also dictates alot about where you land in rankings.
I have seen two sites with almost duplicate links - many from directories and fairly low quality sources. One appeared penalized (a competitor)
After significant research we determined the difference to be that the client site had numerous very high quality links from top notch media.
I think those types of links 'raise the threshold' in terms of the level of low quality links - a balancing out, of sorts.