The best way to know is to understand the correlation between quality score and CPA in your account. You can do this by simply pulling a keyword report including the quality score, doing a pivot table with QS at the right and then a column for calculated CPA and trend line. That will show you if generally you see better CPA on keywords with better QS. Now both Google and Bing provide details on your QS’s attributes, it can assume your attention to those details is more important.