I like vaseline soaked cotton balls (and wax soaked) for starting fires, but I wouldn't discount the fatwood sticks, either.
I carry a stick of fatwood, about three inches long and a little thicker than a pencil, as a key fob. It's totally waterproof, and fairly shockproof. There are no potential issues about tearing aluminum foil, or wearing out foil from extended carrying, or having vaseline melt in the heat and mostly leak out, etc. It's enough to start a few hundred small fires.
The cotton balls are easier to light, but the fatwood shavings are easy enough to light (once you really learn how too do so properly) that lighting difficulty is a non-issue for me.
Fatwood is pretty easy to find in most Northern coniferous forests. The equivalent to vaseline soaked cotton balls is also usually readily at-hand. (Take your knife and scrape cotton lint from your t-shirt and/or blue jeans and/or underwear, rub some lip balm/sunscreen/antibiotic ointment into the lint, and you're set.)
I don't carry pre-made vaseline soaked cotton balls. My psk includes a large swath of "Packtowl" (serves multiple functions: insulating scarf, bandages, sling, water collector, firestarter, etc.); you can pinch it and pull off tufts which light as easily as cotton; and my psk also includes antibiotiic ointment (which comes in a petroleum jelly base), and other "fuels".
I also usually have a couple ounces of 99.99% pure methanol on me (it's a cleaning supply for my camera gear), and nothing else I've found (not even cotton) lights as easily from a spark as that.
I'd consider the fatwood stick a more reliable firestarter than vaseline coaked cotton balls, , due to the greater durability, more total waterproofness, potential to start more fires, etc.
Mike