Is it even worth submitting to the 100's of PR1 - 3 webdirectories or is it better to invest in a few high PR sites?
Do both, the lower page ranks will rise if the directory owners keep working on them and list quality sites.
You can never know for sure which directories will lose PR and which will gain popularity. So it's worth it to do both, but you can't say one approach is going to work better than another, because there's always an element of uncertainty involved.
Let me share some of my experience in this area having burnt my hands in some & made some positive growth. Never look at the PR first. Look at the relevancy first. If You are planning to buy 4 links, buy one each per month. Don't put all the money at once. If you have a relevant site with a High PR, it is always welcome Try to buy links from sites with good content and traffic (atleast less than 100K alexa) Don't use the same keyword in all the links Don't link to the same page in all links, especially don't just buy links to the home page. Instead, buy links to your sub pages also Wait for atleast 6 months to get some decent results Try and add some fresh content atleast once in 2 weeks Always keep your own domain name(I think you've already taken care of this). All the above are some of the points to be noted for G**gle.
http://www.web-directories.ws They have a TON of free directories and after I submitted to ALL of them (most had no PR at the time) and I got a PR4 because the PR of my listing page went up! Kind of like a free investment..