What is Quality and Quantity? Direct PR8 backlink with the keyword in anchor text from the 3rd screen of the page, for example, is it quality? Or Indirect PR4 backlink from the top of the page? So let's say that QQ (quantity+quality) backlinks are better! 1) Small amount of outbound links per page with backlink to you 2) High PR of the page with backlink to you 3) Direct link with the keyword in anchor text There are some gussing (not mine): 4) Link from the home page is better the from internal pages 5) Many links from the same IP address are not as effective as if they we on differect class C networks
I'd say quantity - and quality (I don't believe that Google will keep the linking algo as it is within the next couple of years.) I think that If you have 200 links from on-topic sites, it is better than having 200 links from off-topic sites, at least in the long run...
Quantity alone works short term, but for long term success you need to anticipate filters might apply and manage your linking strategy around that. A lot of cheap links that count with google now but could be easily filtered down the road is a good short term strategy, but a risky long term strategy. So the next question is, what filters are likely to be applied next?