Yuan Peng Chiang thinks this is interesting:

如果純綷比對數字或字元的話，建議使用switch，因為它只會在一開始的switch括號中取出變數 值一次，然後將這個值與下面所設定的case比對，但如果您使用if的話，每次遇到條件式時，都要取出變數值，效率的差異就在這.

The break statements are necessary because without them, statements in switch blocks fall through: All statements after the matching case label are executed in sequence, regardless of the expression of subsequent case labels, until a break statement is encountered