"What are the pros and cons of a bic vs. firesteel?"
A Bic is quick and easy, can be used with one hand (let's say your other hand was trapped under a boulder!), and doubles as a light. You can also generate some heat in pinch if you CAREFULLY! run it under a loose parka or trash bag. That is a trick every serious caver learns from people who have done it. A candle is better yet, but a Bic works in a pinch. Even if you run out of butane, the sparker can still light a canister stove. When ever darn thing is wet, you can eventually light a stick on fire by holding it over the Bic. But in those cases, you really want a square of wax paper, a small candle, or ear wax smeared on belly-button lint.
The fire steel works immediately after pulling it from a puddle, which a Bic does not. And, in conjunction with a Bic, you have redundancy. I once arrived at first campsite with no Bic. My best guess is that it slipped out of a pocket while double-checking gear in the hotel room. A fire steel would have been SO much easier than a fire drill carved with a SAK Classic!
For me, bringing only one: Mini Bic.
But for how important a fire can be when things start going badly, a fire steel SOMEWHERE ELSE in your system is worth it to me.