The difference or purpose for scalloping is pretty simple:
To increase the distance between the tips of your fingers on your fretting hand from the fingerboard when pressing down strings to reduce fretboard "drag".
Early users of this, Richie Blackmore for instance, did it because of how tiny the frets were on older Fenders. It would literally slow you down.
With modern jumbo frets being as huge as they are, it's almost pointless to scallop above the 12th fret because your fingers won't touch the neck anyway.
Lay your guitar flat and press a string to a fret (don't jam it, finger it normally) and peek between your finger and the fretboard. You'll see varying daylight as you travel up and down the neck.
Hope this helps.