Simply put, the difference is the different capacity and operational!

Standard edition:
FDD-UDD STD support 1.44MB one USB Flash Drive corresponds one floppy disk

Excellent edition:
FDD-UDD EX144 support 1.44MB support 100 dummy floppy disks
FDD-UDD EX720 support 720KB support 100 dummy floppy disks , customize program
FDD-UDD EX120 support 1.20MB support 100 dummy floppy disks , customize program

Com edition:
FDD-UDD COM support 1.44MB support 100 dummy floppy disks , the USB Flash Drive no need to format.