Well in PVE it's great because it becomes an "elemental" attack and it whittles down some creatures that have improved defense vs "physical" attacks. In PVP it's about equal. There are some classes at the higher level armor that can get either increased armor vs elemental or increased armor vs physical like the monks, so that's why I carry two different swords, one physical and one elemental. If I see a monk with a lot of tattoos out comes the physical sword, if they are wearing cloth, out comes the elemental. You know fire burns cloth pretty quickly?
Rangers can get a specific elemental increased armor vs lightning, so a lightning sword/axe or air spells using lightning don't do as much damage, so here once again a Fire sword or physical sword would do the most damage the quickest.