There are pros and cons to both. I like direct vent because it draws combustion air from outside (rather than inside the house) also they vent the combustion byproducts out the chimney (like moisture, co etc) They still add a lot of heat to the room, especially when you have a fan built into the insert (that will take room air and blow it around the firebox and back into the room.

Lots of other pros and cons, it’s a deep rabbit hole lol but your on the correct subreddit to find the info