Jeremy, we shouldn't discuss this in the original thread.
There are latency test measurements in the mailing list archive. PCI and
PCIe cards show better results, IOW less MIDI jitter. There are also
explanations why USB suffers from more jitter.
The point of difference is, if the MIDI jitter is audible. It is! The
measurements might not provide correct results. To measure a system by
itself is a bad test and to measure a MIDI loop in addition is tricky.
Jakob (living in Augsburg) from a Linux mailing list (perhaps LAU or
LAD) years ago send me a board to loop through MIDI and that provides an
audio output, to record the MIDI signal to an audio track. I never had
time and interest to continued my MIDI jitter tests, so I still didn't
use it. I guess this would be a better test, then the latency test.
Howsoever, it's better to use PCI or PCIe, IIRC some USB interfaces
even fail(ed) the latency test that measures a MIDI loop. The USB
interface I own doesn't fail the test, but I'm anyway not satisfied and
use PCI and PCIe MIDI only.
That's it, I can't provide more information and I'm not willing to
search the mailing lists archives.
Regards,
Ralf