oscam-emu - EMU support, SoftCam.Key built in, but place the new keys in /etc/tuxbox/config_emu or /usr/keys. For more info check the git page. Compiled with USB support for (some) external readers
oscam - Standard, compiled with USB support for some standard USB readers. Config files in /etc/tuxbox/config_oscam. Limited support for BISS.
oscam-pcsd - Only for those who use PCS external reader, loads extra libs and modules.
*-latest versions do not come with config files or additional stuff (help, examples). Here, oscam-light is a bit specific as it kicks out USB libs, therefore, probably most interesting for those wo cards or those who do not have use of oscam-emu. By definition, oscam-emu might have a bit slower zapping speed (well, clearing to be precise) unless carefully set up (when to use EMU).
Another reason for 'latest' is that PB backup saves your conf files, so might be interesting when restoring...