> MIDI over USB should be much tighter because the bandwidth is a good few orders of magnitude higher.
"should be" != "is". The Atari ST had a ROCK SOLID MIDI clock and direct, bare-metal hardware access that meant the CPU could control the signals directly, with known precise timing. This is simply not possible with modern operating systems and hardware interfaces because of all the abstraction layers, with attendant time indeterminacy, that have been inserted in between. It's physically impossible to match the low latency and jitter of an Atari ST doing MIDI with a modern system.
"should be" != "is". The Atari ST had a ROCK SOLID MIDI clock and direct, bare-metal hardware access that meant the CPU could control the signals directly, with known precise timing. This is simply not possible with modern operating systems and hardware interfaces because of all the abstraction layers, with attendant time indeterminacy, that have been inserted in between. It's physically impossible to match the low latency and jitter of an Atari ST doing MIDI with a modern system.