VDMX also allows for multiple control data to access the same parameter at the same time (multiplexing).
So while your work around would allow for a single button press to set a hard value, only being able to map one control data (MIDI etc) per parameter means that you'd have to increase your values with the mouse pad and that isn't always ideal.
Plus in VDMX, you can set multiple "Marks" meaning that you could have multiple stored hard values to cue up at the press of a button.
The MIDI implementation (and control data in general), in VDMX is so flexible. Unfortunately the app just isn't stable enough for big shows (and is also Mac only)