Matron Landslide
From what I understand there is, but it is only when you bring Mixbus's FX, EQ,Comp,Saturation into play.
Search down in the Software sub forum, Bapu done a test, you can read the results of that test there, which from memory was no, there is no difference all things being equal. I have Mixbus 3 and 4, but on't really like it, and it's way to frustrating to try and use as a fully fledged DAW.
What I never did was to do a duplicate mix (i.e. Mixbus's FX, EQ,Comp,Saturation into play) and post the results.
For me, I'm happy with the results I get just using the summing engine capabilities of MIxbus over console emulation in SONAR. YMMV.