They both have a damage coefficient, which means the damage they will do depends on your power,weapon strength and enemy’s armor, but generally sigil of air hits harder a single target and sigil of fire hits for less but aoe that means fire sigil is decent only when you fight many enemies at once(that means better in wvw but not that good in pve)
Sigils of fire and air stack,can be triggered at same time and are usually used in bursty builds that you often see in pvp or wvw (thieves and shatter mesmers for instance used to run this setup). That’s why it’s not that popular in wvw anymore(but it’s still very good for that game mode) in pve it’s not that good since you might wanna swap/unequip weapons for different encounters or you don’t want to rely on stacking the sigil to be efficient (also if you happen to go down in a fight you lose all the stacks which forces you to restack the weapon) The problem with sigil of bloodlust is that it’s a pain to stack and you can lose your stacks easily(going into water, dying,switching maps) and if a fight occurs that you don’t have sigil stacked, then you have a handicap also if a gvg occurs it’s considered bm to fight with stacked sigil.
