I have used both during a winter walk through my home village's country side. My DA 15 was paired with a K5. Overall, I think the limited is much more flare resistant than the GR and one thing that convinced me that it was worth dragging around both cameras were the starbursts of the DA15. They really made some photographs. Here, the GR was producing more boring blobs of sun. I think this might be a thing to consider particularly for landscape photography.
However, all the other points are equally valid: The GR's increased aperture will be nice in low light, it's a good second camera, much better than most point and shoots, and it does take stunning photographs, particularly in places where interchangeable lens cameras are banned. So maybe you should get both? Hmmm.
Pentax K5 + DA15
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Ricoh GR
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And here's the GR at a gig: