I prefer a fine diamond sharpener for survival use since they are sturdy, virtually unbreakable, and do not require lubrication, though it doesn't hurt to wash them out regularly. The choices here are between rod or stone styles. Either will do the job, provided you know how to properly use it. It's purely a personal issue as to what works best for you. For those with no experience whatsoever, using a stone seems a bit more intuitive and it seems easier for the novice to control the blade angle using a stone.
Sharpeners come in a range of abrasiveness.
Fine will give a good sharp edge and with a little effort will even bring back a badly dulled or damaged blade. Many sharpeners are available with grooves to sharpen fish hooks, but how important that is for a survivor is debatable. Probably not enough to seek out one if the style you want is readily available without it. EZE LAP makes a number of good lightweight rod style sharpeners in fine abrasiveness which are inexpensive, compact, light and easy to use. The only drawback to these small stones is that it isn't too difficult to slip and cut yourself, since due to their small size your hand is in close proximity to the blade.