I don't see any particular attribute in Sanogo to see why he should start over Akpom now. Physically, I think Akpom is as ready as Sanogo was last season.
Sanogo may have been a free transfer, but for where we want to be as a club, we should never have signed him. To have someone at his age, his injury record and thus so little game time behind him to even be given the chance to be our 2nd or 3rd choice striker for any length of time was reckless. He will never really develop with so little minutes. Also someone like Akpom, if he really is rated by Wenger, should never be sidelined on age alone as it is likely that he will have lost his chance to develop at such a high level when young. I can't think of any attacking players who have made it with us having been loaned out or not been given their shot in the first team when 17-19.