Red Bull is an energy drink containing natural and synthetic ingredients like caffeine and taurine.
One can of Red Bull contains about 80 mg of caffeine, while an espresso has about 64 mg of caffeine. Other ingredients in Redbull also have energizing traits, such as sugar and taurine.
So while Espresso has a stronger, bold, bitter taste, Red Bull might have a more substantial energizing effect in the short run because of the other ingredients. In fact, consuming too many energy drinks in a short time frame (like when cramming for exams) might have very adverse medical effects on your body.