There can be a lot of reading to do about RAW formats and DNG as one of them. Basically, DNG or "Digital Negative" is a RAW format developed by Adobe and put into "public domain". A few camera companies use it, but not Nikon or Canon. Maybe the most important feature of having your RAW files in DNG is that nearly all, if not all, of Adobes products will open those files....even the oldest versions.
The conversion to DNG, as opposed to keeping the camera company's version of RAW, has a variety of advantages and disadvantages. None should have an effect on picture quality.
I see no major disadvantages. It does take time to convert. If you wish to process the DNG in software that doesn’t support them, you better hold onto the
proprietary raws. WHEN you convert could be a factor as every time you update the DNG container, even with a tiny edit, it will be backed up should you have a product that backs up data as it recognizes a change to the file.