I have a moderately updated 5,1 Mac Pro - currently with a generic USB3 PCI-e card providing four additional fast USB ports.
I now need to connect a USB-C device to the machine.
I am not sure whether it is better to use a USB-A to USB-C converter plug or to add an additional (or replacement) PCI-e card with USB-C port(s).
Grateful for any suggestions / ideas etc.
I have some experience with several of the USB PCI cards for the cMPs. If you need USB3 speeds (<500MB/s) The choices are mostly 2-port and 4-port cards. The best cards have an unshared USB port for each device. If you need the faster speeds of USB3.1gen2, you can also get those cards which are <1,000MB/s. Those are USB3.1 gen2 or newer, and they come in a variety of configurations with type A or Type C (USB-C), and port sharing except for the HiPoint unit which is best. When USB3 was fastest, I had a $60 4-port unit from Sonnet. Then I put a 4-port type-a USB 3.1 gen2 (<$100). unit in to replace it. That works well except each pair shares a port. A friend has the 4 socket HiPoint with no sharing. Both our units are typeA, to be more versatile.
So, if your USB external device is a fast device like an SSD, you can double your speeds with a 3.1gen2 card. On the other hand, if its a spinner, or almost anything else, USB3 is fine and there are adapters and adapter cables galore. BTW, specs for USB are all over the place, so run the BlackMagic Speed Test to get real world specs. Most USB3 cables are fine for USB3.1gen2. Beware of booting. No USB PCI card that I'm aware of will allow booting, so you must plug it in to the USB2 ports front or back on the chassis, which are super slow.
Some of the new, tiny portable SSD drives, like the Samsung T5 and T7 work really well for certain tasks. They don't have the SATA SSD limitations (<600MB/s) as they are NVMe based. The T5 works for USB3, but I believe the T7 gets speeds close to 800MB/s with USB3.1gen2, and newer, for just a little more $. Good luck
