Buyers must first distinguish between HDD (Hard Disk Drive) and SSD (Solid State Drive). For bulk storage at a lower cost, HDDs are suitable, but for performance, SSDs offer speeds up to 10x faster. Key specs include the interface type (USB 3.2 Gen 2 or USB-C) to ensure high-speed data transfer, and read/write speeds, which should ideally exceed 500MB/s for SSDs or 120MB/s for HDDs. Additionally, check for shock resistance ratings and heat dissipation materials like aluminum casing to ensure long-term hardware reliability.