I think the Sith are terribly misguided. Their philosophy is flawed to a frightening extent, and their actions in the Star Wars franchise run the gamut from reprehensible to horrifying. Emperor Palpatine is clearly sociopathic. So, how can I say that I think they're less disturbed than the Jedi of the Old Republic? I'll point you back to last week's post on the Old Order and let you decide for yourself.
I see the Sith as the other side of the same coin or the other end of the same Force-using spectrum that the Jedi are on. Both groups take their philosophies on the Force to an unhealthy extreme, (which is why the Force needed to be brought back into balance, but that's another series altogether) and they use opposite but complimentary methods to achieve basically the same level of mystical power through it.
The Sith pay a huge price for their adherence to the Dark Side. Obsession, greed, and anger slowly rob them of most of the things they value. I always thought it was the Dark Side that turned Emperor Palpatine's face into a squished up peanut butter and jelly sandwich too, but apparently that was Mace Windu's doing.
We're supposed to think that the Jedi, who take the longer, more difficult path in their study of the Light Side, are rewarded in the end. I will agree that the Jedi are noble and selfless. Those things can be their own reward. I still don't think the Old Order Jedi were so much better off than their Sith counterparts.
I don't know much about the early history of the Jedi Order. What we have comes from comics, video games, and novels, and there's a great deal of disagreement among fans as to how much of that material can be considered canon. One of the few things in the EU that I like is the older version of the Jedi Code, because it seems much more balanced in its way of dealing with emotion and its potential to pull someone to the Dark Side. Even though I like it, it doesn't hold the same level of significance to me as what we can see in the films.
What I know for sure is that Prequel Era Jedi believed that they could (and should) divorce themselves from their own strong emotions. That any emotion they felt had to be acknowledged and then "let go of," no matter what it was going to lead them to the Dark Side. They were not allowed to have families or strong ties to their places of origin. Even strong friendships could be frowned upon by the Jedi Council if someone rubbed them the wrong way. While these Jedi often preached self-control, their doctrine indicated extreme self-denial, compartmentalization of emotions, and poor self-concepts that contributed strongly to the creation of Darth Tyranus and Darth Vader. The Sith are not in any way healthy, but at least the Sith recognize that emotion is not the enemy.
The Jedi were not bad people. They did a lot of good in the Old Republic, and I have a great deal of respect for certain individual Jedi Knights. I can't think of a single Sith Lord that I can say the same thing about. If I had to choose which philosophy was healthier, though, I would choose the Sith Code over the Jedi code any day.
There's not a very wide margin of difference to me between the Prequel era Jedi Order and the Sith in terms extremist views or emotional health. The Jedi simply had a brand of extremism that was socially accepted. They didn't go around killing and maiming innocent people, and they weren't bent on ruling the galaxy. They just sat quietly in their temple becoming less and less connected to the galaxy. The Sith called a lot more attention to their psychological problems.
And since I'm on the subject of emotional disturbance and calling attention to one's psychological problems, I'd like to invite you back next week to read my views on the Anakin/Padmé relationship.