Liquid cooling radiator is one of the top performance impacting elements of a water cooling case mod. Radiator (or heat exchanger) ability to remove heat from your water loop is directly related to your CPU cooling (and GPU cooling) capability. Longer (high impact), wider (lower impact) and thicker (lower impact) watercooling radiators can radiate more heat and therefore provide better cooling performance, having said that, the amount of air going trough radiator is just equally important, so the final outcome belongs to radiator + cooling fan pair optimization.