Hydrodynamical simulations are now vital tools in aiding and interpreting astronomical observations of galaxy clusters. Simulations can evolve dark matter and gas reasonably well, but still struggle to deal with more complex baryonic processes such as star formation or AGN feedback. This is because these processes span an enormous dynamic and temporal range, and so they are often solved with tunable analytical prescriptions, namely subgrid physics. The choice and tuning of subgrid physics has a substantial effect on the global properties of any simulated galaxy cluster, which means that it is imperative to check the validity of a simulation's choice of subgrid physics before reliable conclusions may be drawn. I will present data from the 'nIFTy cluster comparison series', which compares ten different synthetic galaxy clusters at z=0, each produced by a different start-of-the-art code equipped with its own preferred subgrid physics. By using ~1000 haloes in a 5Mpc region surrounding each cluster, I will show that there is an enormous difference between the synthetic galaxy populations and properties produced by each code. Along with this, I will show that all codes cannot reproduce observed global stellar fractions across all dark matter halo masses, and that these effects are a direct consequence of the employed subgrid physics rather than any environmental effect. I will also briefly examine the extent to which preprocessing is occurring at z=0 in the outskirts of these synthetic clusters.