4-5-1 vs 4-3-2-1
Both shapes use one main striker, but they organize the five players behind that striker differently.
4-5-1
Usually shows a broad midfield five.
It can defend width naturally and keep many players behind the ball.
4-3-2-1
Uses three central midfielders plus two narrow attacking midfielders behind the striker.
It is often called the Christmas Tree.
Where does width come from?
In 4-5-1, wide midfielders can provide width.
In 4-3-2-1, fullbacks often have greater responsibility to advance outside the narrow attacking midfielders.
Central overload
The 4-3-2-1 can place many players between the opponent's lines and around the center.
The risk is becoming too narrow.
Defensive relationship
A 4-3-2-1 can flatten into a 4-5-1 if the two attacking midfielders recover into the midfield line.
Coaching exercise
Use a 6v6 central game plus two wide neutral players. Teams must connect through the central overload before releasing a wide player.