When evaluating heavy machinery, you must prioritize the engine model and emission standards (e.g., Tier 3 or Tier 4/Stage V) to ensure compliance with your local environmental laws. Key performance metrics include operating weight, bucket capacity, and maximum digging depth. For hydraulic systems, verify the use of high-pressure main pumps and valves (often Kawasaki or Rexroth brands) which are critical for the machine's longevity and cycle speed. Ensure the factory provides genuine steel grade certifications for the boom and arm to prevent structural cracking under heavy load.