I've been using a fair deal of sustain junglers and junglers that aren't too sustain heavy, and for the most part I think it is slightly more gold efficient to clear it as much as your sustain allows for.
If the champ you are playing has enough sustain to comfortably do a full clear of the jungle, like Fiddlesticks, do it. I'm not sure if you get more gold, but you definitely get more experience from doing so.
If you are playing someone who cannot afford to clear more than 3 camps on the first clear like, say, you are doing something gimmicky like jungle Garen, then definitely take the three camps and back. At that point, you are at risk of dying in the jungle, and no jungler should ever take that risk.
After that, your back definitely depends on what is going around the map and how much health you have.
If you don't have enough health to do anything around the map, definitely back. You don't get a whole lot from staying out with low health.
If you do have enough health to do something around the map, check the map. Look for any of the following:
-jungle camps to clear (or steal)
-lanes to gank (or countergank)
-Scuttlers to take
-unwarded locations to ward
If you can do any of these safely, then definitely do them. Otherwise, it is likely a good time to back.