Sometimes, it's hard to know what type of connection you should use for specific purposes. Despite the wide number of connection types for one device to communicate with another, which have varied wildly over the years before boiling down to a select few, there are still those who are uncertain about whether to get hardware with a USB connection or Thunderbolt, as one must be better than the other, surely. Of course, with the introduction of USB Type-C, things seemingly get complicated yet again.
A Brief History of USB
Everyone knows that USB is meant to be a universal connection system for devices, and that's reflected in the name: Universal Serial Bus. Created in the mid-1990s, the connection sought to be a standard for all devices, providing power and data transfers at up to 1.5Mbit/s at first, under the initial "Low Speed" mode, before "Full Speed" bumped the connection up to 12Mbits.
While the original standard came out in 1996, it wasn't until the arrival of USB 1.1, and the original iMac, that it started to get popular. USB 2.0 arrived just after the change of millennium, bringing with it a "High Speed" mode for data transfers of 480Mbit/s (it should be noted that real-world speeds were always well below these theoretical peak figures). Users had to wait until USB 3.0 launched in 2008 to see gigabit-level speeds, with the "SuperSpeed" mode providing peak connections of up to a potential 5Gbit/s, as well as power improvements. In 2013, the USB Implementers Forum submitted specifications for USB 3.1, which introduced a new "SuperSpeed+" transfer mode of 10Gbit/s.
For USB 3.0, a feature was built in that makes the more recent versions of the standards backwards-compatible with older releases, so devices on different standards can still communicate with each other, and users don't have to keep on upgrading their devices just to keep them working. What this means is that a device running USB 2.0 could work at its normal speed when connected to a computer via a USB 3.0-compatible port, but not at USB 3.0 speeds. A USB 3.0 device could connect to a system via a USB 2.0 port, but would run at 2.0 speeds. Sadly, this backwards compatibility does not extend to USB 1.1 and earlier, despite using the same physical connection.
Thunderbolt in a Nutshell
While the vast majority of computer users will recognize USB, Thunderbolt is more something associated with Macs, though it does occasionally surface on the PC side of things. Initially developed as "Light Peak," Thunderbolt is a newer connection type than USB, with the first consumer devices hitting the market in early 2011. Combining together PCIe and DisplayPort in one cable, as well as providing power, the standard differed from USB in that it could support up to six peripherals from one connector without an extra hub, by daisy-chaining devices together.
The first version of Thunderbolt offered connections of up to 10Gbit/s per channel, with two channels in total, with it offering far greater speeds than USB at the time of release. By incorporating the DisplayPort signal, and with a physical connection the same as the Mini DisplayPort connector, Thunderbolt lent itself to powering displays, with Thunderbolt monitors also allowing data to travel across the connection to other devices, though its high speed also made it extremely useful for data transfers to external storage.
In 2013, Thunderbolt 2 was officially named, and boasted connections of up to 20Gbit/s. In order to accomplish this, the two 10Gbit/s channels used previously were joined together into a single connection. Despite having the same two 10Gbit/s channels as Thunderbolt 1, the combination of the two made the connection a lot more flexible for devices using the standard.
At this point, it's pretty easy to say which connection would be more useful in a particular situation. Projects and systems relying on high-bandwidth connections would benefit more from Thunderbolt 2 than USB 3.0, though the ubiquity of USB as a whole makes it better for smaller, occasional transfers, such as by a thumbdrive, as well as for lower-bandwidth items like webcams.
The Grand Connection Design
Things get muddier when we start talking about USB-C, also known as USB Type C. Finalized in 2014, the connection aimed to replace the confusing Type-B and Type-A connectors typically associated with USB with a single smaller connection, one that is meant to last for a considerable amount of time as a standard. Notably, while normal USB cables have a rectangular plug with a plastic section on one side, which causes consternation when people have to turn the cable around to make it fit, USB-C will work the same regardless of whether it is plugged in correctly or "upside down," which is to say that it is reversible.
Despite the name including USB, USB-C does not lend itself to a specific "standard," and refers to the supposedly "future-proof" connector. Due to the number of contacts used, the pairs can be used for more than just USB 3.1 connections, making it flexible and able to be used by different standards in "alternate modes," such as Thunderbolt 3.
Thunderbolt 3 ports will use the physical USB-C connector, and provide up to 40Gbit/s of bandwidth, twice that of Thunderbolt 2 and four times that of USB 3.1. Support for HDMI 2.0 and DisplayPort 1.2 is also included, making it useful for driving 4K displays at 60Hz, and can also be used to deliver up to 100 watts of power for charging purposes. Handily, earlier Thunderbolt devices will work with Thunderbolt 3 ports using USB-C connectors, via the use of adapters.
Notably, and confusingly for some, while a USB-based device will connect to a Thunderbolt 3 port and function normally within the USB 3.1 parameters, a Thunderbolt 3 connection will not work when plugged into a USB port, even if it has the same connector.
Some PC hardware producers started to offer Thunderbolt 3 connections earlier this year, and though Apple has yet to release a device using the standard, it is likely to do so as part of a Mac or MacBook product refresh. Apple does already have one device that has a USB-C connector, with the MacBook using it for charging, data transfers, and for video, though only at the slower USB 3.1 connection speed.
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