Technically, Firesteel IS more reliable than a Bic lighter.
That's not to say that Bics are not reliable... because they are. I have never had Firesteel or Bic fail on me.
With that said, the Bic is easier & faster to use IMO. For that reason, I carry a mini Bic as my main source of fire, with some matches as backup.
If I was in a survival type situation, I suppose I would rather have Firesteel because it has a lower chance of failure. However, for my backpacking needs, I take the Bic because it is more convenient.