They both had their plusses and minuses, but I liked being dark side slightly more for one good reason: it finally gets rid of Carth. I would dearly loved to have been able to kill him--of all the party members in either KOTOR game, he was by far the most annoying/useless, IMHO. Honestly, his whining about trust issues got so aggravating that I just left him on the ship except for when I HAD to have him as a party member. I didn't even know he had his own sidequest until after I had beaten the game LS/DS several times, and went online for a walkthrough guide just for the sake of completeness.
Be considerate to others or I will bite your torso and give you a disease!