Aside from increased resolution, one of the biggest improvements is MPE. It allows controlling parameters on a per-note basis. A side effect of this is making microtonal music significantly easier to express, since you no longer need multiple channels to do per-note pitch-bending. MPE support is already probably more robust than MTS (MIDI Tuning Standard,) although I could be wrong on that.
Essentially: for traditional western music, it seems to just offer better flexibility and precision, but it will make a huge difference for microtonal music. Honestly, being able to adjust parameters per-note simply makes sense.
(I am not a musician, just a programmer who has dabbled in a small amount of music software and protocols.)
The only limitation of using channels for MPE is that you can't daisy-chain MPE devices... Which nobody really does anyway (most of my gear doesn't even have a THRU port).
MPE also enables increased expressiveness that new kinds of multi-dimensional controllers such as the ROLI keyboards leverage (new kinds of MPE controllers are shown at https://www.midi.org/midi-articles/midi-polyphonic-expressio...). While MPE is part of MIDI 1.0, many synth manufacturers never bothered to support it since their MIDI implementations were basically considered a "solved" problem by product management. Many of them never even bothered to support polyphonic after-touch except in their high-end keyboards.
Now with MIDI 2.0 support becoming a 'checkbox' item for customers, all the manufacturers will need to revisit their MIDI implementations in upcoming product releases (some already have). I suspect many will use this as an opportunity to increase input dimensions and expressiveness - which is a very good thing for all of us users, even if they do so in ways which may have technically been possible before.
Essentially: for traditional western music, it seems to just offer better flexibility and precision, but it will make a huge difference for microtonal music. Honestly, being able to adjust parameters per-note simply makes sense.
(I am not a musician, just a programmer who has dabbled in a small amount of music software and protocols.)