Both DefilerPak and CCCP basically installs the same core components: ffdshow, Haali's filter, and VSFilter; except CCCP also includes WMV9, Gabest's MPEG2 decoder (not sure why) and two DirectShow players.
CCCP is however, configured in a way so that all the components are fuctioning together in harmony with the players; though I do not know if DefilerPak is configured in a similar fashion. Therefore, I would recommend
CCCP as the most compatible codec pack; but there would be nothing wrong with using
DefilerPak, either.
Packs such as the K-Lite pack or Nimo should be avoided if possible. They install far too many codecs and filters which are also left with the default options, causing compatibility issues. It would be fine if one knew what they were doing and chose the correct components and configured it properly, but for the majority of people who just hammer Next at the installation screen it breaks compatibility.
VideoLAN is able to decode
most formats without the hassle of installing anything else. (And because of this I found it the most versatile in Linux.) But I didn't like the fact that their subtitles were too plain and I never managed to get it to display a small border around the subtitles.
Jam it back in, in the dark.