Not sure about the differences, but I can tell you that the Audiobuddy is a little muddy in the low end, but is fairly clean otherwise. You'll notice this on some things more than others. Unless you can afford something better, you should probably just go with the Audiobuddy untiil you can. That's just my guess.

The Audiobuddy is supposed to produce less than 48v phantom power which may effect some mics. The DMP is based on the same Burr Brown INA 163 chip as the Grace 101. I don't know if the Audiobuddy is or not, but I doubt it. What does that mean sonically? I'm not sure, but a lot of people over at homerecording.com with considerable experience with low-midrange gear (including the RNP) think the DMP3 was "designed right." The DMP3, IMO, sounds better than the RNP on acoustic guitar--at least on the mp3s I have heard. In real life it has a clean, not sterile sound (dare I say warm) and produces excellent stereo imaging compared to a Behringer mixer. You can get them now for $149, so I think it is well worth the xtra money