[moredial]

Only 2 points to take into consideration:
1. Google penalises affiliate sites
2. Google rewards sites with adwords

As a high score is closely related to high ranking, the easier option is to improve the overall page content to rank higher in the natural results and take your ppc campaign to one of the many other merchants who still work on a bid price rather than charging you more because they don't want you as an advertiser.

I know that is a simplistic view. But, if you do a leaflet distribution for £100 you know what size your ad will be, where it will be distributed and how many will be distributed. With G you give £100 and can run out before your target market have woken up.