When evaluating pico projectors, the most critical factor is Brightness (measured in ANSI Lumens); for portable use, look for at least 100-500 ANSI Lumens to ensure visibility in low-light environments. You must also verify the Native Resolution (e.g., 720p or 1080p) rather than just 'supported' resolution. Additionally, check the Light Source Life, typically DLP or LED technology offering 20,000 to 30,000 hours of operation, and the Battery Capacity (mAh), which should ideally support 1.5 to 3 hours of continuous playback.