Well, regarding the firepiston I can tell you it is a very reliable fire starter with an infinite number of lights.
That should be a consideration.
Granted, the technique must be learned (still easy enough for anyone to master in very little time, though).
But then again, everything must be learned, no excuse to knock firepistons for that. But still, many people have opinions based on nothing whatsoever. Was any of us born riding a bicycle, or did we have to learn how to do this at some point ?
Not really a reason to dismiss bicycles as not usefull now, is it? See what I mean ? I carry a mini firepiston as well as a few other fire starting options. I can have a coal in seconds on the first or second try, guaranteed.
Also a coal is longer lived than a spark and doesn't blow out in wind or draft. Wind only makes it stronger. I carry my FP loaded with tinder so it's always ready to go (this is a waterproof setup too!).
It will light numerous natural tinders and you can char cotton or any other natural fibre and even tiny pieces of wood in an altoids-tin in your campfire (thus creating charcoal for FP tinder). By doing so you can endlessly replenish your tinder supply in the field.
So, there's a few reasons for the FP.
Hope this helps.
Regards,
Pharaoh