USB 1.1, while NOT bi-directional, has a max speed of 12 Megabits, which is in another class entirely. Even having to send stuff in one direction at a time in serial order, when part of the MIDI system it's still by far the fastest part and is never a factor in MIDI timing as long as the MIDI is properly buffered and timed on each end.
what do you mean by properly timed... at the receiving side?
USB's only "fault" here is that it's a what-should-be-unnecessary conversion in the middle of the stream.
plus that the connection bidirectional and if someone tries to share yet another device at the same bus, you never know how the transfer rate is limited.
then, in USB, those bidirectional bursts of usb data are limited to a 1 ms clock. sure, that is quite a lot, but it is possible to hit the border when using midi in realtime expecially with multiple interface at that same usb port.
furthermore, in USB each 3 MIDI bytes require 32 bit of space and more data will only be send within the same burst when polyphony comes to play.
and the requirement of an usb device driver (in most cases - especially under OS9) is also not so sexy.
The SXPRO is no faster than using the USB port via a Keyspan 28X and jitter is a non-issue in MIDI.
in theory it makes huge difference if you can send stuff in time but limited to only 31kbaud - or if you have plenty of bandwidth but can only send 1000 packages per second.
however in practice you are right, because there is always only MIDI DIN on the other end anyway.
in the last online discussion about better or worse MIDI connectivity somebody recently posted a bunch of graphs showing the latency of devices: a waldorf microwave I or oberheim matrix 1000 sythesizer for example has a latency of 3 ms - which will rise up to 9 ms for the 10th voice i.e. when 9 voices are already running.
that kind of ended the discussion about how to connect interfaces to PCs in order to get nanosecond accuracy.
one will only get it when all synthesizers are able to receive time tagged control data, which is synced to their audio rate. which is about what you can get when working ITB.
