It depends on how you get hit and how do you land. Cars builders have pedestrian safety in mind as they get NCAP ratings for it. If you are lucky, maybe not that much damage. On the other hand full frontal collision with a bus is probably not good for you as there is nowhere for you slide or bounce off to lose some of the energy. Bike is similar to bus as there is no way for you to 'gently' (no 'soft' metal to bend or curves to steer you off it) lose some of the energy.