Hi
I am currently doing A2 for both of them.
Personnally I would do the one you find easiest or are more fluent/ talented in as it will make your life a whole lot easier. For me the easiest is French, because the grammar is more straight forward and you don't have to think as much about things like word order as it is pretty much the same (except for word + adjective).
Apperently the new curriculum that starts in September makes you write an essay on a book for the 1st year and in the 2nd year book and history (on the 2nd WW) essay questions. SO you might also want to think about which language you would prefer to read it in and get the gist of the story better, and also think about whether you know the more about German or French history during WW2.
Anyway I really enjoyed both of them and I hope you'll enjoy which ever you choose. Hope it helps ;9