Johan Helsingius suggests that I compare the Chordite and the Twiddler. There are two possible comparisons: between concepts and between implementations. So, the concept first.
The Twiddler uses several three keys for each finger, and two keys for your thumb. Various combinations of these keys generate keystrokes. The Chordite uses the thumb to hold the keyboard. Since the Chordite keys are pressed by the knuckles rather than fingertip, each finger may press one or two keys.
In both systems, each finger can generate two bits of information. Twiddler can press Left, Middle, Right, or no key. Chordite can press Distal, Medial, Distal and Medial, or no keys. However, the Twiddler includes two buttons for the thumb, so that makes the chordspace four times as large. The Chordite makes up for that by providing for sticky shift, control, and alt prefixes.
The implementations differ because the Twiddler 2 is a USB keyboard, and my Chordite is bluetooth. Since the Twiddler 3 will be bluetooth, there's no obvious benefit to the Chordite.