This information applies to version(s): 1, 2
DxO PureRAW can only work on RAW files, whereas Dfine from Nik Collection only accepts RGB Data such as TIFF and JPEG.
Regarding DeepPRIME Denoising vs. Dfine from Nik Collection denoising: when possible, any Denoising should be done on a RAW file. DxO's AI-based DeepPRIME applied in tandem with Demosaicing delivers much better results and offers the highest image quality results.
Dfine from Nik Collection will be good on RGB images that are already in JPEG and TIFF, and especially on a local correction.