For me both Nketiah and Balogun are currently more or less level in terms of value. We only have to look at Lacazette last season to put the level of League 1 into context. I see his performance of last season as little different from Eddie being record goal scorer for England under 21. Maybe Balogun has more potential - we haven't seen him in the EPL, but to counter that, while Nketiah does not appear to be top 4 level, he at least has a track record of playing there, and was useful for us when used as a starter.
Eddie is used to how we play, wants to be at the club and for good or ill is liked by the Manager. Balogun's value could easily be the highest its going to get, so the sensible move would be to sell him.