On Prince diffculty and up the barbs PREFER to attack the human over an AI. I have witnessed many times barbs spawning 5 tiles from an AI city but the barbs will walk about 20 tiles to my territory to attack me because of the altered values on higher difficulties. (Another reason why I wouldn't say the GW is cheating.)
I highly doubt that the barbarians let up on the AI on prince difficulty, especially since noble, one level below, is supposed to be completely neutral for both parties in terms of advantages.
Things that the barbarians do prefer or workers and improvements to destroy, weakened units and badly defended cities.
I tried Raging Barbarians for the first time last week. I had the perfect starting location and was setting up a great civ on Prince. Then the next turn there were 8 warriors on the screen. Then about 4 more added each turn thereafter. I had to shut down production on my two cities and start researching Archery. It was fun battling them while trying to build settlers and keep my workers and improvements protected. In the end I held off the barbarians but the other civs had passed me by in techs and cities. My 5 cities to their 10. Are the AI's not affected by Raging Barbarians?
Yes, it does indeed. If you read my post a bit earlier in the thread, you would see that I point out how it greatly hinders the AI development until people have grown together enough to prevent most barbarians from entering the lands. Of course, I play extremely big maps (279 x 186 normally, three times the size of 'huge'), on noble difficulty, so there will be more barbarians and more isolated players. Generally, a few AIs who have been close togther or develop good military early have done quite well, while most only have a chance to catch up later.
I suppose, if you play on prince, the advantage that the AI gets will have a much greater effect with raging barbarians on as well. When I play on noble, I see raging barbarians as a little too much help for me since the AI players will be badly developed and I will do well, just getting a little more starting experience. After a few games, I understood the importance of getting a horse or copper resource early, and after that they haven't ever brought me to the brink of extinction. Regardless of how I fare, they are still great fun to fight and there are moments where they are quite scare and the great wall looks awfully good.