tf2 has so many game modes. pub, mge, 6v6, 9v9, pyro dodgeball, dm, bball, jumping, surfing, etc.
pugs, lobbies and scrims/matches differ vastly even though they follow the same formats. some pubs/pugs/lobbies are more serious than others. you can pugscrim against actual teams and have an atmosphere that is much different from both pugging and scrimming. it's great.