Raichu can't use the Light Ball. And Raichu still has higher total base stats. However, it would have lower Attack and Sp. Attack, so Pikachu is sometimes used more often as a Sweeper.

Raichu IS stronger, tougher and more durable than Pikachu in the games. The only down side is that Raichu can't use the Light Ball but regardless it still has higher total base stats. However, it would have lower Attack and Sp. Attack, so Pikachu would generally be the better sweeper.