Having just completed a project involving nineteen piano pieces, the majority with accompaniment, I had plenty of opportunities to try different sampled or modelled instruments for the various virtual ensembles.
Using modelled instruments in Wallender's WIVI gave me very satisfying results, mainly due to the smooth transitions between dynamic regions and the response of the instruments. The one thing lacking for me was the mechanical and performance noises produced by the player. I'll quickly explain before your mind goes in the wrong direction.
The breathiness of the flute, or the clicking of the bassoon's mechanics, for example, are all part of an intimate performance. The harder edge produced in a sound when accents are needed, is another example.
The basic sampled instrument sounds of a DAW may cater to this, but not often. A multi-sampled, velocity switched instrument will have various layers to emulate different dynamics of playing, so playing technique needs to be refined for the purpose of accessing these layers.
In my last project the parts were already played into Cubase, and because the original player didn't have access to the same sound library, the parts were not as accurately played to utilise dynamic layers. Unfortunately, this meant that certain opportunities were missed when it came to the expressiveness of the accompaniment. The beauty of working with MIDI is that the problem is easily fixed!
If you look at the image of the Cubase Key Editor (or Piano Roll in other DAWs), you can see the played notes on screen, and their relevant velocities along the bottom. If you select the pencil tool you can redraw these velocities with a quick stroke, or drag the top of the velocity line up or down to hear the various layers available. You can also adjust note lengths on this screen.
When I'm working with this screen I like to loop four or eight bars and adjust velocities on the fly, listening to the results in context on the the next loop around.
Remember! If you are presenting an audio version of your composition for the consideration of a listener/investor/collaborator, spending some extra time on making sure the accompaniment works well with your main instrument (and sounds realistic) can make a big difference.