Value of a link can be determined by this. 1) is this link relevant 2) cached in google / yahoo / msn (becauise if it's not cached then it's almost useless to get linked. If search engines don't know your link is there then you'll not get any benefit. 3) Total number of put bound links 4) Total number of inbound links 5) Avoid linking with site which has more than 100 outbound links on one page.
Maybe it would be best if you check the both of the websites to see if their which qualities are better then the others. To me, quality pages > high PR pages.