Interacting with the plugins via VST automation allows for a generally superior experience.
A couple of advantages that stand out:
- better resolution/precision
- bi-directional communication pretty much guaranteed
Especially the bi-directional communication matters for automated faders and displaying current plugin settings on the hardware controller.
Many great plugins only receive midi control messages, but do not send them. But they will receive AND send VST automation messages.
And Cubase (and any other host that) facilitates bi-directional midi to vst automation communication generally makes it a much better experience for all of those plugins that don’t send midi.