Helen,
That's a loaded question and here's why. It depends on how you prepare and convert the file. I use Silver Efex mostly and I can replicate my tonalities of my Leica's and Tri-X. Both cameras can do that because of the processing but....
There is no comparision between the 2 as far as certain things in IQ. The DP1 is as good as it gets....I prefer it to my M8's and everything else because it has a certain GRIT in the appearance of the print. Darkroom GRIT.....
The files are very analog and organic and that's why I prefer working with that.
The GX-200 is a joy to use and the files in DNG are very good. It has a different tonal range out of the camera due to the size of the sensor, obviously. The definition/detail is not as defined because of that also...but it has GRIT. I need that in my images...it's a quality that visually an image of mine has to have. My M8 is almost pristine, so is the D300, 5D and all the large sensor cameras. They read digital where as the DP1 and now the GX-200 of course are digital but are not sterile....I hope you understand and I'm sure you do...
B&W can't get much better than working with these 2...of course I am really just starting out the journey with them but it's off to a good start...
If I could only have 1 it would be the DP1 because of it's responsiveness and speed of working,
luckily, I am not in that position and I have both...
later...shooter