However, both generally want a lot of levels in the class to get good amounts of the bonus damage; +1d6 isn't all that much, you want those +3d6 and +8d6 numbers. That's why I wouldn't suggest picking the skill class based on the precision damage they deal.
This is also why I suggest going with the Martial Rogue variant if you use Rogue; Martial Rogue loses Sneak Attack but gets Fighter bonus feats. This way you get skills + feats; as you noticed earlier, Barbarian can benefit quite a bit from having a lot of feats so bonus feats are really helpful.
Basically, Ranger is Full BAB while both Rogue and Scout lose 1 BAB so Ranger is the "Full BAB + skills"-option. Also, if you have any level in Ranger you can use Wands with Ranger-spells in them (for example, Wand of Cure Light Wounds for out of combat healing) which can be helpful, a nice small bonus (yes, this even works if you don't have enough levels to cast Ranger spells).