The video mentions smaller hitbox, but a smaller character model also gives you more ability to see around your character from the 3rd person camera perspective. When I played World of Warcraft, I chose the man model of the largest race (for the racial bonus) and wore bulky plate mail body armor as part of my character class. I realized it was hard to see whether I was standing in fire or other ground effects. Watching other people play, I noticed that it was easier to see whether you are standing in bad stuff if you chose to play a woman human character, and much easier if you played as a gnome. I chose to start using consumables which made my character model visibly smaller.