In Ableton Live, when using VST plugins that send MIDI data, it is necessary to use two tracks. One to place the VST plugin and another where the MIDI data sent by the VST plugin is received. This is often inconvenient as it requires switching from one track to another while working.
With MIDI VST it is possible to use VST plugins and instruments on the same track. It works within an Instrument Rack, where it automatically sends the MIDI data from the VST plugin loaded in the first chain to the other chains in the rack.