In general, I think fire is good in PvE if you know for sure that you're not the one tanking because then all you need to do is spam consistent non-stop damage which fire does very easily. Lightning seems better if you're tanking because it has high burst potential in very short intervals, so it helps you maintain aggro DPS while making the most of your chi consumption, while fire DPS relies on uninterrupted prolonged DPS intervals. I've been thinking fire might be good in PvP to kill cats because of the basically infinite chi rotation and doesn't rely on Heaven's Blade or crowd control for damage, but I'm too lazy to try it.