The Ultimate Box writes as many designs to The Ultimate Card as it can hold- 225,000 stitches. The Ultimate Box also reads designs from unprotected cards and saves them to the hard drive of your computer. Amazing Box and Magic Box will not save anything to your computer, and only download up to 6 designs to the card.
Download and use designs from the Internet (often for free) or buy them on the floppy or compact disks, then transfer them to your machine with rewritable card included.
Works with your Brother, Baby Lock, Bernina Deco, Simplicity, White and Viking #1+, Iris and Rose
Writes to the Ultimate Card, Amazing (Magic) blank card and 512K (4 Megabit) Blank Brother card
The box connects to the serial port of your computer.
Can be used to transfer/format images that were downloaded
Supports the following formats:PES, PEC, HUS.
Works with Windows 98 or newer operating systems with a serial port
The Amazing Box 2 is upgrade

Thanks Red for explaining this. I did buy the Ultimate Box instead of the other two and now I know why and I'm very happy with my Ultimate Box. I erase and copy to my card almost daily.