I think it depends on who you are playing. If you are with a champ with strong early presence like Lee, Elise or Evelynn, you should be focusing on ganking instead of farming!!! while other junglers (weak gankers pre-lvl6 or late game champs like nasus) can tolerate to farm much more instead of ganking. And there are others like J4 or Vi who can do whatever they want in both jungles as long as they are farming, ganking or screwing the enemy jungler.
Many people say that the one of the reason C9 is so effective is because their jugnler have a solid flux of gold and exp. He only goes to lanes if it's a sure gank, a sure counter gank, or enemies have recalled and you can do a 3 man push on the turret until laners are back.