Can anyone tell me how much of a difference it actually makes in Googles eyes that you trade links with say a PR 3 site as opposed to PR 1 when they look at ranking your site for search purposes?
It's hard to tell. Assuming that all other things are equal (content, OBL, relevance, indexed pages, link positioning, anchor text, etc.) the PR 3 site will carry some more weight. However, if you are TRADING links, the value of the link is diminished anyhow.
Thanks, im new to affiliate marketing and im just curious as to how much I should be concentrating on what PR rank sites have that I trade links with in order to push my sites up the rankings in Google.
PR is just one part of the equation - you need to also look at the quality of the links pointing to that site and also the number of outbound links on the page where you link appears. Also, the PR value that appears in the toolbar is rather approximate. If the toolbar states "PR3" the page could be a lot closer to a PR2 than a PR4 (and vice versa).
It is difficult to give you a specific answer. Google PageRank is a factor of SERP. However, it is unnecessary to pay much attention to PR. When trading links, if I have chances to make a choice, I tend to choose the sites than can be updated regularly.
Theoretically, all other things being equal you will get more PR for trading with a page that has a higher page rank. However, as we all know, all other things are never equal. The SEO gurus I respect the most say don't rely on link trading if you can possibly get relevant one-way links to your site. In other words, it always comes back to authority, do people want to see or refer to your content? in the long run, everything else is pretty much irrelevant.