IRL, I find the Sith philosophy to be more appealing because it's basically about embracing your emotions as a part of who you are, rather than repress them out of existence through self-denial.
However, in a universe where the force actually exists, the Jedi are absolutely right and the Sith are idiots.
See, force sensitivity in Star Wars is actually kind of a disability. An ordinary person can pretty much do, think or feel whatever they like and still retain a degree of autonomy and psychological health. A force sensitive cannot. Once a force sensitive becomes angry, or frightened, or feels any of the emotions it would be totally normal for a person to feel, they run the risk of drawing on the dark side. When they do, they will suddenly realize that a whole new source of power is available to them, an incredibly easy source of power. They suddenly feel euphoric and amazing, like they can do anything.. as long as they keep drawing on the dark side.
Then over time, very subtly, they come to depend more and more on the dark side. In fact, they become less and less able to draw on any emotion or power not of the dark side, and the sense of power they feel starts to feel less and less sufficient. The only way they can make the feeling of power come back is by behaving in accordance with the dark side, by constantly being angry, by constantly killing things, by nursing their festering hatred of everything. All the emotions they used to have atrophy away leaving only a vicious cycle of self-loathing, compulsive behavior and rage.
In case it's not obvious at this point, let me spell it out. The dark side is space crack. That is why the Sith are absolute idiots, that is why they constantly sabotage themselves through compulsive displays of petty, mindless evil. That is why they can't work together or accomplish any lasting goals. That is why their interesting philosophy essentially boils down to being angry all the time, because they aren't in the driving seat any more. The dark side is in the driving seat. They go where it wants, they do what it wants, they feel what it wants. They're the broken shells of human beings being driven around by their addiction.
If I was in the Star Wars universe and happened to be cursed with force sensitivity, I would definitely side with the Jedi. The Jedi teach voluntary self-restraint, which is regrettable but understandable. The Sith teach false freedom in order to disguise their involuntary servitude to their own power.
Some Star Wars stuff, most notably the Old Republic games, have a much more shades of grey understanding of the force with this very dualistic notion of balance. How canon you consider that will vary, but even then it doesn't really fit with the depiction of the Sith even in those games.