Let’s be fair. Why do people want Double USB? Price per GB.
If you are on a budget and only doing sequential video logging (not random data dumps), the USB setup is cheaper. However, you lose the "double space" efficiency because you cannot span the volume. sdata tool v100 double usb or sd card space better
Conclusion: For space AND performance, Double USB is objectively better – provided you use a powered USB hub. Without external power, the SD card wins only in convenience. Let’s be fair