Starise
I think I would prefer a plug in to moving files and working between apps.
Using the routing options available on the new MOTU interfaces I could actually manage to route the Sonar buses to Mixbus INs ... no bouncing, start transport in Sonar, mix in Mixbus ... however, that was a while ago and due to lack of time I have not pursued it any further so I can't tell about the true downsides (the obvious one would be no fast bounce)