you can tell by the way he dribbles that he's naturally left footed, his posture is similar to Giggs' or Robben's.. my theory is that left footed players have different (and better) shooting technique than right-footers.
Oba has shown lethal finishing with both feet, which is amazing really.. when he came here i thought he was more of the Rossi type, who'd rather twist his legs in the most unbelievable ways just to avoid using his weaker foot..