I have a fire piston, although I've not used it much. Mine needs to be lubricated with vasaline or similar. I can imagine running out of vasaline when I still had tinder. Also, I think the device has a minimum size in order to work; anyway, mine is physically large and too big to carry.

I like the Sparklite, especially as it is so small. I believe anything which makes sparks is good because it can be used with improvised tinder.

Similarly the Sparklite tinder is good because it can be used with anything that makes a spark or flame. In fact for a while I was using them with a ciggy lighter for lighting hex fuel, because I found that worked easier than the lighter on its own. (Nowadays I use tinder card for that because it is cheaper, but QuickTabs are better because they are more waterproof.)

Currently I reckon the best bet is a flint-ignition lighter. When it has fuel it's the easiest thing to use, anyone can understand it and it works one-handed. Liquid fuel ones have the drawback that the fuel evaporates, but the advantage that it is easier to replace the fuel eg with meths or petrol which is likely to be available in my urban environment. Imco models seem less prone to evaporation than Zippo. When the fuel runs out, you can hope to improvise tinder for the spark.