Quote: PEF is the pentax proprietary RAW format. DNG is an open RAW format that was created by adobe but could be used by anyone.
there should be no quality differences between the formats, and unlike JPEG's, which are created after post processing the RAW file a DNG is not processed.
i don't usually shoot RAW (i have my own, good reasons for this) but if i did i would definitely save DNG's rather than PEF's because DNG's will be supported as long as adobe is around. PEF support on the other hand is not guaranteed and gets complicated with different versions of the format (different cameras, different firmware versions, etc).
i just found out that none of the big players, nikon, canon, or sony have native dng support which is too bad because consumers would benefit from a single, well supported raw format.
When I got Elements v6, I had to get the (free) newer ACR for it to recognize that camera. Simply put the file in the "plugins" directory.
PEFs are slightly smaller than DNG, and obviously the Pentax software, as well as Elements, Fastone and others open it just fine, so I would not worry about it being obsolete anytime soon. You can also simply convert them in a big batch if needed.