Exporting Bus Question

Is it better to export just using the Master bus or What I Hear" in the export options screen? Normally I have all busses routed to the master so I'm assuming all I need to do is export just using the Master Bus.
 
Reason I ask is ... I installed the demo of Ozone and was trying to figure out how to use it's dithering instead of Sonar's and it got me thinking about exporting and busses and which ones dithering applies to.
 
Is everything in the buss area dithered or just the bus (or busses) with outputs set to your sound card? I really never thought about this too much until I tried out Ozone.
 

I always do master buss because it is more consistent. With dithering you dither in Ozone and not in export. In the end it probably doesn't matter where you do it or if you do it at all.