[member="Darren Torran"]
Alright, let's see here...
Dark Jedi lack ideology: they have essentially moved away from the path of the Jedi (and may, indeed, never have been Jedi to begin with). Their approach to the Force is fairly instinctual: think the D&D contrast between a Wizard (one who studies and trains in Arcane arts) vs a Sorceror (one who gains their gifts through natural ability). The Dark Jedi uses their emotions to reach for their powers (in a very natural fashion), and though they
may train to advance their skills, much of their skill is inherent and contextual. They are likely to be very emotive individuals, but are not beholden to any ideology. They can be raging torrents of psychopathy, or reasonable individuals who simply seek to better themselves. With a Dark Jedi, the spectrum is
all over the map. They can be whatever they want, and simply harness the powers of the Force to that end.
I will note that, despite their name, they need
not be beholden to the Dark Side of the Force: there can be Dark Jedi who practice with the Light in the way that a Jedi might, but unlike a Jedi, they need not live according to the Jedi's codes and philosophies. Around here, that's classified more as a
Rogue Jedi, but it's not an entirely appropriate label, any more than Dark Jedi is.
Sith, on the other hand, are beholden to an ideology, and to the Dark Side primarily. Most of them are Imperialists, and believe in establishing the rule of law and order over the Galaxy, with the Sith at the head. They are
Social Darwinists, and believe that strength (though not necessarily physical strength) empowers them above ordinary beings, and demands that they rule. They are pragmatists, and believe that they should do whatever is necessary to further their cause. They are not anarchists or simply out to see the Galaxy burn (though some will eventually become sufficiently corrupt that they head that way), but rather they are out to further the Sith cause: supremacy above all things. There are rules, codes, philosophies that they must ascribe to. And though they will usually be far stronger than any Dark Jedi, this power comes with a significant price:
pain. To train as a Sith means to be broken, to be exposed for a weak being, and built back up again.
That doesn't even touch on 1/10th of it, but I'll save myself some time accounting it all and just link you to the guides written on the topic: