Is USB or Thunderbolt better for portable SSDs? The key differences, explained

I could spoil this entire article and tell you right off the bat which high-speed bus protocol you should be looking at for you current and future external storage needs… But where’s the fun in that?

If you need an answer right away, simply scroll to the bottom and grab your instant gratification. Otherwise, educate yourself with this quick treatise on the various high-speed external protocols that are available, as well as their respective strengths and weaknesses.

10Gbps USB (USB 3.2)

So, have we really come so far that a 10Gbps/1GBps transfer rate seems quaint? I’d say, yes, at least from the perspective of a long-time storage reviewer. Nevertheless, for small amounts of data, a 1GBps transfers rate is still going to get the job done quickly enough.

And, of course, for a lot less cash than the 20Gbps/40Gbps options. If capacity means more to you than top performance, then 10Gbps USB (or even 5Gbps if you really don’t care about speed) could be the way to go.

20Gbps USB (USB 3.2×2)

This protocol offers fast 20Gbps transfers, but it’s the odd duck of the bunch. It will work on normal USB ports at reduced 10Gbps/5Gbps speed, but a dedicated and not particularly common 3.2×2 port (sometimes referenced at 20Gbps) is required to attain the promised 2GBps transfers.

Another downside is that unlike USB4, USB 3.2×2 will not function at its full 20Gbps on most Thunderbolt 3 or 4 ports, instead dropping to 10Gbps — the rate of most native USB implementations. Thunderbolt passes through USB to the system.

That speed drop afflicts all new Apple Silicon Macs. I was sorely disappointed when I found out that my more-than-fast-enough 20Gbps USB SSDs transferred at half speed on my otherwise stellar-performing Mac Studio.

On the plus side, 20Gbps USB SSDs run cooler, use less juice than their 40Gbps counterparts, and still gets things transferred pretty darn quickly. The price of USB 3.2×2 SSDs has dropped some recently, due to USB4 showing up, but they’re still not as affordable as a 10Gbps SSDs.

Thunderbolt

While Thunderbolt has been the de facto high-speed port on Macs for well over a decade now, it’s not nearly as widespread on Windows PC platforms. Largely that’s because it’s pricier to implement than USB thanks to royalties and greater power delivery. That goes for both motherboards and drives.

Thunderbolt is certainly more common than it once was, but it’s hardly ubiquitous on the Windows side of the pond. Here are the various flavors you might run across.

Thunderbolt 1/2: These older versions with Mini-DisplayPort connectors and 10Gbps/20Gbps transfer rates are only found on legacy equipment, though you can connect newer Type-C Thunderbolt peripherals to these ports and vice versa using Apple’s Thunderbolt adapter. There are others, but check the specs carefully — some don’t connect 1/2 to 3/4/5, only vice versa.

My advice? Stick with newer Thunderbolt 3/4/5 peripherals and use the adapter. Or perhaps upgrade your computer.

Thunderbolt 3: This version of the technology doubled bandwidth to 40Gbps and was the first version to use the Type-C connector. The latter confused just about everyone, as USB switched to this connector around the same time.

Thankfully, Thunderbolt 3 tunnels USB so you may attach USB peripherals to a Thunderbolt port, if not the other way around. Thunderbolt 3 can achieve around 3GBps during transfers on most computers sporting the technology. It’s also getting cheaper as the industry moves on to Thunderbolt 4/5.

Thunderbolt 4: 40Gbps Thunderbolt 4 was more a certification update than a change in the technology. Intel found that vendors weren’t implementing all of Thunderbolt 3’s features all the time. Thunderbolt 4 made implementing the entire stadard mandatory if you wanted to use the name and logo.

Thunderbolt 5: Version 5 doubles version 3/4’s 40Gbps storage bandwidth to 80Gbps. You may see 120Gbps mentioned in slides, but that’s downstream only to drive displays.

Thunderbolt 5 also delivers significantly more power across the bus at 240W as opposed to Thunderbolt 3/4’s 100 watts and the mere 9.9 watts of 1/2. This makes Thunderbolt 5 the go-to for power users with power hungry storage peripherals — e.g., a RAID box.

But wait… There’s a caveat! While Thunderbolt 5’s specs sound spectacular and it benchmarks great, it hasn’t shown a significant impact on real-world performance in our real-world large file transfers.

Also, the doubled bandwidth does nothing to speed random performance, which is far more about seek time than raw throughput. So it won’t run an operating system appreciably faster than an older Thunderbolt 3/4 SSD.

USB4

As you may or may not be aware, USB4 is basically a version of Thunderbolt 4 that was donated to the USB Forum by Intel. Hence there’s an awful lot in common including the up-to-40Gbps transfers. The ace up USB4’s sleeve is far greater compatibility.

While you can’t attach Thunderbolt peripherals to older 1/2/3.x USB ports, you can attach USB4 peripherals to those ports with every expectation of them operating. Of course, only at the maximum speed of the older port — but hey, better slower than not at all!

Also, the shared heritage means you can attach a USB4 peripheral to a Thunderbolt 3/4/5 port and have it work at its best speed: 20Gbps on Thunderbolt 3 and 40Gbps on the other two.

If almost complete compatibility weren’t enough, USB4 seems to be coming to market at a lower price point than Thunderbolt 3/4/5. Adata’s uber-fast SE920 is roughly $125 per terabyte, about par with no-name Thunderbolt 4/5 SSDs. Alternatively, you can grab a USB4 enclosure such as UGreen’s CM642 for less than $100 and add your own NVMe SSD.

Note that there is an 80Gbps USB4 2.0 in the works (of course there is!), but we haven’t seen an implementation yet.

USB4 for the win!

If you just read all of the above, it shouldn’t surprise you that I’m giving the nod to USB4. It’s very fast, compatible with just about every computer and device on the planet, and more affordable than Thunderbolt.

The only exceptions to that recommendation would be 5/10Gbps USB if you need something super cheap, or Thunderbolt 5 if you want absolute top performance and have the software and hardware to take advantage of it.

Further reading: Best external drives