DP1 at ISO 1600 vs. GX100. My bet is on the Ricoh.

dc.watch have just released their SD14 review and you really got to see it to believe it.

http://dc.watch.impress.co.jp/cda/review/2007/04/26/6159.html

The high ISO is amazingly bad.

SD14 at ISO 1600
http://dc.watch.impress.co.jp/cda/parts/image_for_link/93156-6159-17-2.html

R5 at ISO 1600
http://dc.watch.impress.co.jp/cda/parts/image_for_link/71116-4846-14-3.html

GX100 at ISO 1600 (note that the entire GX100 ISO series is out-of-focus, but still the noise looks way better than that of the SD14)
http://dc.watch.impress.co.jp/cda/parts/image_for_link/91171-6073-21-3.html

And here are the shots, downsized to 800x600 and without any noise-reduction applied.

SD14

R5

GX100

And 100% crops:

SD14

R5

GX100

And finally, the same crops with Noiseware applied (as best as I could):

SD14

R5

GX100

Bottom line: With f/2.5 lens, IS and less splotchy ISO 1600, the GX100 is going to be far more usable than the DP1 for any low light shooting. In fact, so would the R5/R6.

Prog.