You will hopefully get comments from other than me, but…
1) If you plug an external pedal into a MIDI controller, you may encounter the same issues as plugging an unsuitable pedal into an H9.
2) There is a risk with a MIDI pedal of a slight "rubberiness," due to the indirect connection. Depends on the pedal.
3) On the bright side, it frees up the AUX socket.
