i prefer barbs off
barbs will be more a problem to some players due to their random placement, this can have significant impacts on early development, and that effect snowballs considerably.
so in the interest of testing skill and not map luck i prefer barbs off. Civplayers civ league always play barbs off, tho no quitters play with them on for reasons stated.
barbs also add processing and therefore lag, as do any ai element like citystates. i reduce citystates also btw, and often remove them also as again random placement causes imbalances.
I find that the early game buildup is quicker when you dont have to build extra units, and making a multiplayer game go quicker is worth it imo.
barbs off means human civs fight on a more balanced basis.
yes it means some civs lose an ability but montezuma is imbalanced again on a barbs map esp raging.
I' d like to respond to your post. In my opinion skills are tested with barbs on. You have to have minor level of defense to manage barbs. If you go on building great library or whatever without establishing a military presence, barbs will act in balancing fashion, damaging your resources and slowing development. Which is fair, again, in my opinion, to other players and the AI. If you have skills, you'll fend them off and prepare your military for inevitable strike from AI or human, or just go about questing.
Picture this multiplayer game. Pangaea. Two players start next to each other, third one is distant. Switch off barbs and the distant player gets massive advantages, since no one will go after him and leave own borders unprotected.
The buildup can, actually, be only a fraction slower, and in most of my games even faster WITH military. If you kill a barb camp near maritime CS - you will grow faster, gaining higher production. Kill one near culture CS = More culture = more happiness, other bonuses, etc, etc. Early CS alliances give the biggest effect in the early game.
In my SP space race games i built all space parts before turn 250 consistently, some games were faster. Don't think i'll get much different results by just solving 'the barb problem'. There would be new advantages and new disadvantages, if i would switch them off, so i keep them.