assuming a ful vog cub set is used with fire resistance maxed. which one is more effective.
I can't really comment on the combuster part because I haven't used it, but for Fang of Vog, most of the time it's not worth using. I use it a lot just because of the novelty, and the charge up attack is extremely strong. If it didn't light you on fire it'd be amazing. It's viable in Tier 2, but once you are in Tier 3 the fire just adds up too much (I even try to carry around remedy potions 24/7). The regular auto hits from Fang of Vog are absolutely awful, in my opinion. It's only real use is the charge up, which as I said earlier, just isn't worth it most of the time. I won't lie, it is quite nice vs Trojans, you can literally one shot them with the charge up, but still it doesn't warrant enough use for me to keep it over some other items. It's more just for fun, ALMOST very good, but the self-induced damage hurts (I have full fire resist). Others with Fang of Vog feel free to correct me.
Combuster. Funny how the hardest weapon to obtain in the entire game is so easily outdone by pretty common/easy to make ones.
So, let's compare.
Fang of Vog:
-Less attack. Obvious here.
-The speed meter looks the same for FoV and Combuster, right? Wrong. Fang of Vog is much slower, even though it shows the same speed.
-Less range? Haven't ever tested but FoV is really small. It shows less range than the Brandish lines.
-Charge attack is a 360, has incredible damage and can hit up to four times. This can be devastating against undead and construct. But at what cost?
--1/3 chance of being set on fire. Even with maximum fire resist.
--Even with maximum fire resist, you'll be taking 1 - 1.7 damage a tick, three ticks in total, (total 3 to 5 bars of damage) over 5 seconds of fire. This is on T3 - certainly not viable for constant use. T2 is a bit weaker, only being able to deal up to 2 bars of damage total - Somewhat usable as long as you don't spam it like a madman.
-Normal attacks have a quite high chance of fire. (20%, I think?) It's a nice additional damage, but fire is already pretty useless, so it does not matter much. It's about as powerful as a medium damage bonus would be. A bit less or more, depending on the mob race.
-Ridiculously hard to obtain.
-More attack power.
-Easier to obtain.
-Can have UVs.
-Will not set yourself on fire.
-Charge is ranged. Although it's not as generally powerful, it can be more useful since you don't have to moderate your usage of the charge.
So pretty much, Fang of Vog ends up being something simply for showing off you've killed Vanaduke a lot. Combuster is the actual decent fire sword.
Fang of Vog could really do with some buffs, considering it's the hardest weapon to obtain in the game.
Ddog and Biz summed it up nicely. I actually prefer the Glacius over the two if you want an ele sword. The only reason I keep the FoV on me is because of its looks. It's a DVS/WHB on fire :O
Glacius/Combuster look like tuning forks lol