Depends on activity, length, weather...
Bic lighters are small, cheap, tough, light and reliable. Good for a few days out nor far from civilization. Because it's only good enough to light something, but it won't work if wet, or even moist, it will quickly heat and you won't be able to hold it in your hand for long, it won't work at high altitudes, and it'll be hard to light anything if there's wind.
Matches, in all their forms, are quite good, and can at least provide a decent flame without burning your fingers within 2 seconds. Considering stormproof waterproof light anywhere matches are a thing, pick these. Though they may refuse to light for no fucking reason.
Flint is waterproof, can produce sparks in any condition, and is the most reliable fire source there is, though the least practical of all. Picking this as your main fire source is fucking retarded, but this should always be your secondary fire source. Considering the weight and size of it, you should always have one on you.
Storm proof lighters are the most convenient fire sources, but prone to failure, though much less than Bics, and in a different way than matches, because they you still have a flint. Can provide a continuous flame without burning your fingers.
Fuel ones leak but that's how they work, butane ones don't but are generally cheaply built and as a result leak just as much, except they don't work at all then. Thus fuel ones are superior. Won't work better than matches in many conditions, but at least they will always produce a flame whereas matches may not. Anything that burns can be used as lighter fluid: if you carry a stove, or even vodka, then you have lighter fluid on you.
So Bics for short hikes, real lighters for guaranteed flame, matches for easier flame in many conditions, and always flint.
