FormerlyHemlock
Hero
The same level spell Bless gives +D4 to hit for 3 PCs. For a 5 PC party with an average of 50% chance to hit a fairly tough foe, that's an increase of 15% more damage per round. Since Faerie Fire gives everyone Advantage (+5 to hit in the 50% case, but usually ~+4.5 to hit), that's an increase of 50% more damage per round. More than 3 times as powerful as Bless. Granted, Bless is not limited to just the targets in the initial area of effect, but then again, Bless doesn't find invisible foes.
In that case, Bless is 25% more hits, not 15%.