Quoting Roger Ford: The MM one is a great lightweight jack - ideal for transporting to race meetings or track days.
The Arcan looks like it might be a better garage jack - it's quick-lift and goes significantly higher (508mm vs 375mm). More money, though.
The height gain is significant, and for the sake of an extra £30-40 quid over the long term, plus the extra lift capacity, that's why I went for it. It's pretty big though; agree that the MM one would be better for mobile/track use unless you've got a full support van!