Buyers must prioritize Generation Compatibility (DDR3, DDR4, DDR5) as these are not backward compatible. Key metrics include Frequency (MHz), where higher speeds like 3200MHz or 5200MHz command higher margins, and CAS Latency (CL), which defines performance efficiency. For high-end gaming or workstation builds, ensure the RAM supports XMP (Extreme Memory Profile) or EXPO for easy overclocking. Additionally, verify the IC Brand (Samsung, SK Hynix, Micron), as these 'Big Three' manufacturers determine the underlying stability and quality of the module.