I think I may have figured out the pros and cons of Track Instruments vs. Rack Instruments.
Both allow you to:
- Route multiple MIDI tracks to the same VST instrument
- Access instruments on different MIDI channels within multi-timbral instruments such as Kontakt and Omnisphere
- Use the multiple outputs of VST instruments
Track Instruments have one advantage as far as I can tell: If you use the new “Visibility Sync” feature of Cubase 7.5 to sync the Arrange window with the Mix Console, whenever you click an Instrument Track, its audio fader will be selected in the Mix Console. The same thing does not happen when selecting a MIDI track routed to a Rack Instrument.
The big disadvantage of Track Instruments for me is that you apparently can’t name your Arrange page tracks something descriptive like “Bass” without also changing the name of the corresponding audio fader in the Mix Console. I prefer to keep my audio faders named after the VST Instruments themselves. For instance, I would prefer to see “Omnisphere” as the fader/track name in the Mix Console rather than “Bass”.
It’s a subtle distinction that will probably either be lost on most people or not matter one way or the other.