What is the priority for the new Adwords campaign functionality "optimize ads for conversions", CTR, conversion rate or conversion volume?

Your question highlights a few problems with Google's automated advert delivery optimisation. In your example, the adverts have generated 9 conversions from 120 clicks. This is not enough to draw any conclusions, but because Google tries to be helpful and serves one advert more than the other, the test can take much longer to complete. If you had 60 clicks on each advert, and one was converting much better, then you'd be a lot closer to a significant result. Were your figures from an actual test? If you're looking at a date range when both adverts have been running, it's interesting that the higher volume of clicks came from the advert with a lower conversion rate. Possibly, this is due to click through rate, or it could be a case of Google showing the established advert more often than a new test version - again, this can skew results. I would recommend that you set adverts to rotate evenly, and monitor the results yourself. When you have a significant result, then remove the weaker advert and test a new one. In addition, I'd suggest that optimising purely to maximise conversion rate may not be the best objective. For the sake of argument, say that you are paying £0.20 per click, and that a conversion is worth £20 to you. Assume also that the difference in clicks is due to the second advert filtering unwanted traffic, and both adverts had the same impressions. Advert A has generated £100 for a cost of £20 (profit of £80), and Advert B has generated £80 for a cost of £4 (profit of £76). In this case, you may prefer to go with Advert A. Average order values could also be affected by the advert text or landing page, and this may also be worth taking into account.

B will be shown since it is having higher conversion rate and campaign is set to show ads having higher conversion rate.