Sideswipe is true to his function of Warrior. Though proficient with guns, he prefers melee combat to ranged weapons, and will employ any maneuver it takes to get close enough to the enemy to use his arm-mounted Cybertanium swords. His agile, wheel-legged form more than allows for this. His tactics are merciless and he's utterly unapologetic about this—war, after all, is messy.
Oh, and he's also not vain at all: those alt modes of his are chosen for speed only.