Both (sorry!), there are known factors that the collisions are different, but also actual are actual statistical probabilities of different things that can happen when **exactly** the same initial condition occurs. And then there are even more random things like angles, the created particles can essentially fly in any direction after a proton-proton collision. Producing all those random options is one of the reasons we use very advanced simulations to predict what we expect. A substantial fraction of the grid computing power is used to produce those simulations.