I don't think Martial has the full set of ingredients to play either of those roles effectively.
He doesn't have the killer instinct or appreciation of movement to be a CF. And he doesn't have the final ball or workrate to be an inside forward.
What he does have is a lot of raw talent. Great finishing, very good close control on the run, decent upper body strength with his back to goal, and excellent pace. But there's a lack competitive edge which prevents him from bringing it all together. I have no idea what the best thing is to do with Martial. Mourinho, Ole, LvG and Deschamps have all failed to coax the best out of the guy (at least so far).
I reckon he could be brilliant in a midtable team scoring 25+ goals in a season. Like a Danny Ings or Kevin Phillips who had their teams built around them. There's a lot about Martial that gives the impression he's top class. But doing it at a big club may be beyond him.
I'll be hoping for a penny drop moment in the meantime.