Play with touchgraph and you'll get a feel for site clusters. I'd really like to see a touchgraph merged with Yahoo site explorer data expanded out three or four linking nodes, now that would be illuminating.
Is one way linking more valuable or less valuable then link exchanging
no. it is not more or less valuable. they are the same, as far as the value of the effect of the link on the website in the SERPs.
However, one-way links are a lot more expensive to obtain and to retain. Thus, dollar for dollar, direct reciprocal link exchange has the best value for your dollar in that you can get a lot more recips that you can get one-ways for the same amount of money.
I will probably be attacked for stating the above by SEOs (some really big names out there perpetuate the myth that one-ways are more valuable than recips) who find it too difficult to manage and make money from reciprocal links, when they can simply buy one-way links for their clients and get a cut of that spend every month. One-ways are a lot less work for the SEO and a lot more money.