There was a time when I was pretty intent on getting one of these. Since acquiring the Roland DC-30 (analog delay and chorus) I've been significantly less interested. Never the less, I'll talk briefly about the differences between the two.
The SDE-100 has a red digital display and slightly more analog-type controls (the same amount of knobs though). The SDE-200's design is a little more modern, but it has that great greenish-blue digital display. That display was the main thing. I thought it would look really great glowing in my studio (bedroom) at night. Now, I'm not so sure. Too modern? Perhaps. How does the sound compare? Don't know, everything sounds same.