Prefacing this with I don’t know much about this stuff:
I just bought a house and the vent did basically this. Issue was it back drafted into the sofets and made the attic still moist and there was mold. Without knowing what you’re doing I think out the roof is the best.
I second this as one should be careful where you vent moist air. My dryer vent in the winter would draft up into my soffits as well and it caused mold. Instead of fixing the issue I just replaced my gas dryer with an all in one washer dryer that condenses the air into the drain pipe and pumps it into the drain.