SanDisk Optimus GX 7100 NVMe SSD vs SanDisk 520 SATA SSD

The Optimus GX 7100 is the faster drive by a wide margin: it is a PCIe NVMe M.2 SSD, while the 520 is a SATA 2.5-inch drive capped at 560 MB/s read and 525 MB/s write. Buy the GX 7100 for a modern desktop or laptop with an M.2 slot, especially for booting Windows, large game installs and video work. Buy the 520 if you have only a 2.5-inch SATA bay, want a simple drop-in upgrade for an older machine, or need extra storage without touching the M.2 slot. Both carry a 4.8 rating from owners, so the real split is interface and speed, not reliability.

• Choose the SanDisk Optimus GX 7100 if your system has an M.2 slot and you want the fastest everyday boot, app and file performance.
• Choose the SanDisk 520 if you are limited to a 2.5-inch SATA bay or want a low-hassle upgrade for an older laptop or desktop.