FireLine has no stretch, so hooksets are much better. It also is much stronger than a monofilament line of similar diameter.
Six pound test FireLine is the same diameter as two pound test monofilament. That’s a big advantage! With FireLine crystal it is possible to use a strong line that is nearly invisible. When that walleye is analyzing your lure as it hangs in the water, it won’t be spooked by your line.