I've mostly prefer dark, but it is true that you come to a much better area of philosophy, when you take some of it from both sides. Such as the idea that if your killing someone, not just for yourself, but in killing them, you change something that now may not seem to matter, but will in the future.
Both sides have their strengths, and weaknesses. Even if you do chose to follow the light or dark side in the game, one of Kreia's comments at the end does put what you truely are in perspective, even if you have a preference of sides.
And as much as i do prefer the light over the dark, (after all, it is somewhat satisfying to be able to get a few more credits, some items, or anything, merely with a bit of manipulation.) both sides have certain things that call people to them. Ether you are after power, supremacy, or if you are just looking to help went needed.