While I can find speed ratings for USB 3 (600 MBps), lot of articles I read about USB-C start with "it depends". Some mention transfer speeds of up to 10GBps, while others claim that it's like comparing apples and oranges.
So for the specific use case of purchasing a hard drive enclosure, what are the speed differences between USB 3 and USB-C?
USB-C is a connector specification.
USB 3.x is probably mainly a signalling specification.
USB-C (formally known as USB Type-C) is a 24-pin USB connector system with a rotationally symmetrical connector.
The USB Type-C Specification 1.0 was published by the USB Implementers Forum (USB-IF) and was finalized in August 2014. It was developed at roughly the same time as the USB 3.1 specification. In July 2016, it was adopted by the IEC as "IEC 62680-1-3".
Read more at...
ref: https://en.wikipedia.org/wiki/USB-C
Some mention transfer speeds of up to 10GBps, while others claim that it's like comparing apples and oranges.
It is comparing apples and oranges. USB 3.x is a communications protocol and USB-C is a port for power and data. I use "3.x" to encompass the different versions of USB from 3.0 to 3.2. USB-C is a port that may or may not carry a USB 3.x signal. USB 3.x can use ports other than USB-C. The transfer speed of USB 3.x depends on the version and connector. The transfer speed of USB-C depends on the protocol. One can't compare the speed of one to the other because they describe two different aspects of a data channel.
So for the specific use case of purchasing a hard drive enclosure, what are the speed differences between USB 3 and USB-C?
I'll be a bit imprecise to keep this short as this can get complicated quickly.
USB-C is capable of 40 Gbps, perhaps a bit more, but with protocols other than USB 3.x. USB 3.0 is capable of up to 5 Gbps, USB 3.1 up to 10 Gbps, and USB 3.2 up top 20 Gbps. USB 3.x can use many kinds of ports but on a drive what you will want are those with a USB-C port, micro-B port, or captive USB-C cable. A drive using anything other than those three will likely be junk. Getting more than 10 Gbps requires USB-C, but not all drives with USB-C will be able of more than 10 Gbps so check the specs.
I like drives with USB-C or micro-B ports as opposed to a captive USB-C cable as I can choose the right cable to plug into a host computer with either USB-A or USB-C ports. There are certainly adapters for plugging drives with captive USB-C cables into computers with USB-A ports but these are to be avoided. Such adapters violate the USB 3.x spec and so their wiring is not standardized, they may work, they may not, they may damage your hardware and start a fire. So, buy the right drive for your needs to avoid an expensive mistake.
Not all USB cables are equal. Some USB-C cables will be rated for only USB 2.0, some for only 5 Gbps, some for 10 Gbps and others for 20 Gbps. Those rated for USB 2.0 will have only the USB trident icon on the connectors. Those rated for 5 Gbps will have the "SS" icon with the trident, and maybe a small number 5. Those rated for 10 Gbps will have a 10, and those rated for 20 Gbps will have a 20. Because of details that get complicated quickly a 10 Gbps rated cable will almost certainly work at 20 Gbps but don't count on it.
Of course the speed will be that of the weakest link. To get the most from your drive choose the right cable and check that the port on the computer can handle the speed.
Again I left a lot out to keep this short. There's nearly a dozen different USB ports but you should only care about three of them, USB-A, micro-B, and USB-C. There's different "generations" of USB 3.x but that can be safely overlooked in most cases, what you should care about is the rated speed of the drive, cable, and host. A USB compliant cable will indicate the speed it has been tested for on one or both ends of the cable, and the drive should list the maximum data rate in it's specs.
