If you think PR is that important you might want to reevaluate your thought process. Google 'Porn' and you'll see sites like
http://www.wedigporn.com/ listed on page one which are PR0. Google is no longer updating PR frequently or reliably. There are also a ton of PR2 and 3 sites that haven't been updated in eons selling and trading links at high prices based on their PR when they don't even rank in the top 100 for any meaningful SERP.
Yes, two equal sites where one has a higher PR, I'd go with the higher PR site. Same with Alexa. However, the idea that Alexa or PR on their own are significant stats just isn't accurate anymore. Google figured out the only people who found PR useful were link buyers and SEOs trying to game the system, so they stopped providing useful information that way.
There are plenty of PR0 sites I'd rather get a link from than many PR1,2 and 3 sites I have seen lately. You'll be much better off finding PR0 sites that update, rank well, have good bounce rates, have original content etc... than you will with a link farm full of popups that make users leave the page faster even though it happens to be PR1
