I'm thinking barbarian culture farming might be a viable early game strategy but I can't seem to find exactly how much culture is rewarded for barbarian kills vs encampment takeover.
Dispersing a Barbarian encampment awards no culture, only gold.
If you have the Honor policy, and kill a Barbarian unit, you get an amount of culture proportional to the strength of the unit. I believe this is 50% of their strength, although I believe it's something they've adjusted previously.
Montezuma of the Aztecs gains a similar bonus for killing all units, and these two culture bonuses stack.
The underlying question you're trying to answer is "is it worth it to farm Barbarians for culture?" The answer to this depends on the amount of Barbarians and the amount of farming you can do. In general, if you want culture, I'd suggest either Liberty or Tradition instead, since they both provide flat culture-per-turn. Barbarian units don't tend to spawn fast enough to beat the amount of culture you'd get from these other policies.
If you're going down the Honor track for other reasons, then the answer is "possibly" - if you're not at war, and have more military units than you need to defend your borders, you may as well farm them for the small culture bonus.
Do note that if a camp is near enough to a body of water that naval units will spawn, there is a cap on how many units a camp can have active at once. Thus, you'll have to destroy the naval units if you want more land units.
Also note that the AI doesn't really think about or care about farming Barbarians, so they will often march up and wipe the camp off the map, taking the gold and leaving you culture-less. :(