I think it depends on a number of things:
1. The length of the talk. If you only have 30 minutes then your talk will be considerably different from a 50 minute talk.
2. What did the job emphasize? If they specifically discussed one area that you do then I would focus on that and weave in your other research.
I struggled with this a little and I actually asked the chair if they wanted to hear more about A or B. They said A (and I could tell this from the questions they asked in the phone interview). So I'm going with a strong emphasis on A, highlighting some very specific things they wanted from the job ad/phone interview…and I'm going to weave in B towards the end and discuss all the studies from B as one big study (it all came from one big study, but multiple pubs).
My future directions are all related to things they emphasized in the phone interviews.
Of course, the next job talk may be completely different if they wanted an emphasis on area B.
Go with your gut and what YOU will be most comfortable presenting.
Also remember…an overabundance of detail from one study will likely put an audience to sleep :-)