When evaluating water radiators, you must prioritize core material and construction. For high-performance needs, aluminum cores are preferred for their superior heat dissipation and lightweight properties, while copper-brass is often chosen for its corrosion resistance in harsh environments. Ensure the fin density (FPI - Fins Per Inch) is optimized for the specific airflow; higher FPI increases cooling surface area but may require stronger fans. Additionally, verify the pressure rating (typically measured in bar or PSI) to ensure it exceeds the operating pressure of your system to prevent leaks or bursts.