One of the great things about the MIDI Supertracks is being able to use a vst instrument to get the same performance that a RealTrack provided.
Particularly (for me) the pianos.

In a recent song, I used 3 different sources for a piano track:
An EZKeys track and 2 different BIAB MIDI Supertracks.

Since they are all MIDI, I could apply the same piano module (the EZKeys Grand in this case) to the combined performance.
If I had tried to use the EZKeys wav (export) and the 2 BIAB RealTracks they would likely all sound different.

If there is a MIDI Supertrack available for a piano RealTrack, I always go with the MST because I can control what the piano sounds like. I have a number of good vst pianos and they all allow parameter tweaking. And I find that many of the piano RTs have effects on them that do not work in my mixes.

It also allows you to edit the performance - which is not always possible with the RT.

If you want, you can hear the 3 track example I referred to here:
https://www.pgmusic.com/forums/ubbthreads.php?ubb=showflat&Number=618149&page=1

150+ Songs produced using BIAB RealTracks
And 50 more...
and some more...