Hard to light birch bark or a candle with a spark. Not true of the vas/cotton option.

Scrape the bark with knife to make fluff first and it'll catch, but candle, no clue how to light that with firesteel.

Birch bark lights easily from a fire steel...if you know the proper methods. As for the candle, I carry 3 methods of fire starting (fire steel, wooden matches, BIC lighter) at all times so a candle is still a viable option for me.