Well plenty different legally. Difference between a felony and a misdemeanor. Doesn't matter really. Will probably get thrown out because of police mishandling, and if not, pardon by the governor as he's already suggested.
For a number of states, the weapon being functional or not does not change the status of charged crime; robbery with a fake weapon can still carry the same punishment as robbery with a real one, for example.
I'm not sure if Missouri differentiates or not. Also, since the charge is assault(IIRC) the weapon's status may play more of a role than if it was a "menacing/threatening" charge.