Choosing between DDR4 and DDR5 RAM is one of the most consequential decisions you will make when building or upgrading a desktop PC in 2025. The memory market has shifted decisively: DDR5 is now the standard for new platforms from both Intel and AMD, yet DDR4 remains widely available, cheaper, and perfectly capable for many users. This article provides a factual, evidence-based comparison of DDR4 and DDR5, covering technical specifications, real-world performance, pricing in the Taiwan market, platform compatibility, and practical buying advice. Whether you are assembling a budget gaming rig, a high-end workstation, or a compact mini-ITX system, understanding these differences will help you allocate your budget effectively.