If you are looking at Audiolab products, here is the distinction:
If you are working with an ASUS or MSI motherboard, you may notice two identical 9-pin internal sockets labeled and USB_E34 . Choosing between them can cause hesitation, but the truth is simple: there is zero functional difference between USB_E12 and USB_E34. They are identical internal USB 2.0 headers, and you can plug your cable into either one without affecting system performance or safety. usb e12 vs usb e34