Enigma and Neutrino are like the base code of the image. Most images are either enigma based or neutrino based.
Gemini is an enigma image. PLi, DK, Nabilo, CLi, Nemesis, Merlin, LT, etc - these are all enigma images.
RuDream are the only dreambox image creator to make a neutrino image. Others have promised but never quite released one. You see 'Cryos Neutrino Image' - this is a RuDream image modified by Cryogenic.
Basically the only difference is the look and style of the GUI. The functionality is the same. If you've had a Dbox2 you'll know what neutrino looks like and if you've had a dreambox, the images are mostly enigma.