I've noticed that file size is greatly reduced when converting from MLV to DNG (say, 4.77G MLV becomes only 2.56G DNG, and so on). I'm using MlRawViewer to convert files.
The question is if there's any redundant data contained in MLV, or do I lose image quality when converting? Does it make sense to store large MLVs for archiving purposes, or DNGs are good enough?
MLV: Uncompressed data.
DNG: Various compression modes. Lossless, uncompressed, lossy.
If you are using lossless compression (the only option implemented in MLrawviewer) there is no difference in IQ.
The MLV format itself supports compression (just not in camera). You can use mlv_dump to compress MLV files. See also the MLVFS thread.