Objectively the Goblins are stronger here. As I mentioned, actual rewards are not the issue or the argument I am making, simply who would make the stronger ally at first glance.
So what if the goblins are stronger than the druids? This still doesn't make them strong enough to be an interesting option to ally with, except if you play as Astarion. Because he is the only character for whom the alternative is worse. But for everyone else? The absolute cultists are blissfully unaware that they are just being used, and might end up as either food or mindflayers. As such, they don't even have valuable information on how to get rid of the tadpole before you end up same as them.
