In the phrase “as long as an Equipment named . . . is attached to a creature you control,” the “you” is the controller of the Equipment, not the controller of the creature it's attached to. Suppose an opponent controls a creature equipped with Bride's Gown and another creature equipped with Groom's Finery, and they also control both of those Equipment. If you gain control of one of those creatures but not the Equipment attached to it, the creature you gained control of will get all the bonuses and the creature they control will only get +2/+0.