The iceman carried a bowstave,ax,load carrying backpack,belt pouch,3 flint impelints,a bone awl,tinder,and birch fungi.
The trebuchet is larger (thus making everything else better, like a child throwing smaller rocks at a shorter distance than an adult can). The system is also designed better, the catapult uses stored elasticity to propel the rock, whereas the trebuchet uses a heavily weighted beam which is lifted and stores gravitational energy, while the long sling holds the rock. The leverage of the beam which is close to the pivot point against the long sling which will thus move faster propels its ammunition at an even faster speed than a catapult ever did. Hopefully this answers the question.