Emphasis on "working". If your BIC works, sure, use it. It will be easier than a firesteel. It's when your BIC doesn't work that you'll be glad you have a firesteel. A firesteel is not "a replacement for", it is "an addition to".

I do find firesteels better than BICs for lighting things like alcohol burners or propane BBQ grills. You don't have to get your hands down there as close and risk getting burned.