It comes down to a more personal choice.
Dark Side seems to be easier and quicker for a lot of people and they are looking for a fast way to become powerful. Some people also are more prone to anger and jealousy (and that can be in regards to anything) and so it is easier for them to go darkside.
Light side is a more difficult choice to make. You have to be aware of your emotions and try to remain in control and look at all angles of the situation. This is not easy for most people. This has to be a conscious choice in facing decisions.
I believe the reason some chose dark side over the light side, not that is is more powerful, just that is is quicker and faster for them. They don't have to look at what they are doing, they just react in any given situation.
People confuse light side in being weak but in truth it is not. To me it takes more strength of character to look at a situation and see what you should do instead of just reacting in the moment. Is it easy to do? No, it is very difficult for a lot of people.
At least that is my opinion.
Extremely good points. But the thing is, self-discipline is not the same as power. When I say power, I mean as in raw Force power. It just takes more self-control to stay Light Side. But am not talking about self-control, but outer, physical strength.
But joining Dark Side to get power "quicker" as in trimming a couple years off training? Doesn't make sense. There's more to the Dark Side ideology for that. Jedi get power fast as well, since they can fight as Padawans even as a small child.