Critical strike champions are forced to choose between Guinsoo's Rageblade and Infinity Edge. Both of these increase your 20% critical strike chance. While Guinsoo's Rageblade gives attack speed, Infinity Edge will provide a source of extra damage. Generally speaking, Guinsoo's Rageblade is more popular among champions who have proc abilities or rely on attack speed, while Infinity Edge scales better for characters who need attack damage.