To (perfectly) solve 9x9 go, you need to consider almost every move at every turn. That's a branching factor of 40+. In this game, there are (usually) at most

To (perfectly) solve 9x9 go, you need to consider almost every move at every turn. That's a branching factor of 40+. In this game, there are (usually) at most 9 legal moves per turn. The branching factor is a lot less. (Giving your opponent free choice to play anywhere is frequently a mistake.)